@conference {644, title = {Caloric and spin transport profile of Fermi-Hubbard systems}, year = {2023}, month = {6{\textendash}10 Nov 2023}, pages = {P.16}, publisher = {Asian Network School and Workshop on Complex Condensed Matter Systems 2023}, address = {IOP VAST, Vietnam}, abstract = {An open one-dimensional Fermi-Hubbard optical lattice exposed to external electromagnetic fields is investigated using the grand canonical ensemble formalism. As the system was reduced to a dimer, the eigenstates were determined using the exact diagonalization method while tuning the two-particle interactions of the lattice, a varying chemical potential, and applied external electromagnetic fields. Entropy and heat capacity gradients exist due to the interaction of the system with the external magnetic and electric fields, also known as magnetocaloric and electrocaloric effects, respectively. At particular temperatures, the isothermal entropic change was calculated to determine the necessary conditions for direct or inverse caloric effects to occur. The effects of more lattice sites and the elastic two-particle interaction can be incorporated through analytical methods. It was shown that at low temperatures, spins tend to scatter under the influence of repulsive two-particle interactions, while backflow occurs in the attractive regime. Furthermore, suitable temperature ranges for spin conductivity to occur can be found by adjusting the electromagnetic fields.}, url = {https://iop.vast.vn/asian/2023/program.php?t=1\&n=16}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @article {618, title = {Causal structure of interacting Weyl fermions in condensed matter systems}, journal = {Nat. Commun.}, volume = {14}, year = {2023}, pages = {2228}, abstract = {The spacetime light cone is central to the definition of causality in the theory of relativity. Recently, links between relativistic and condensed matter physics have been uncovered, where relativistic particles can emerge as quasiparticles in the energy-momentum space of matter. Here, we unveil an energy-momentum analogue of the spacetime light cone by mapping time to energy, space to momentum, and the light cone to the Weyl cone. We show that two Weyl quasiparticles can only interact to open a global energy gap if they lie in each other{\textquoteright}s energy-momentum dispersion cones{\textendash}analogous to two events that can only have a causal connection if they lie in each other{\textquoteright}s light cones. Moreover, we demonstrate that the causality of surface chiral modes in quantum matter is entangled with the causality of bulk Weyl fermions. Furthermore, we identify a unique quantum horizon region and an associated {\textquoteright}thick horizon{\textquoteright} in the emergent causal structure.}, doi = {10.1038/s41467-023-37931-w}, url = {https://www.nature.com/articles/s41467-023-37931-w}, author = {Wei-Chi Chiu and Guoqing Chang and Gennevieve Macam and Ilya Belopolski and Shin-Ming Huang and Robert Markiewicz and Jia-Xin Yin and Zi-Jia Cheng and Chi-Cheng Lee and Tay-Rong Chang and Feng-Chuan Chuang and Su-Yang Xu and Hsin Lin and M. Zahid Hasan and Arun Bansil} } @inproceedings {627, title = {Classifying compressed physics article abstracts by locality-sensitive hashing}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-1H-05}, address = {Siargao}, abstract = {Data is often irreversibly converted into hash codes for storage and processing. Since hashing compresses text so that the original content is no longer readable, many conventional text classification techniques can no longer be applied to them. In this study, we demonstrate that a similarity search technique known as locality-sensitive hashing can be used to accurately classify hashed abstracts from the arXiv repository. Models like these can be used to recommend subject class labels for new or uncategorized physics article abstracts.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-1H-05}, author = {Daquioag, Alyana S. and Francis N. C. Paraan} } @article {660, title = {Critical points in coupled Potts models and correlated percolation}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2023}, year = {2023}, pages = {013203}, abstract = {We use scale invariant scattering theory to exactly determine the renormalization group fixed points of a q-state Potts model coupled to an r-state Potts model in two dimensions. For integer values of q and r the fixed point equations are very constraining and show in particular that scale invariance in coupled Potts ferromagnets is limited to the Ashkin-Teller case (q = r = 2). Since our results extend to continuous values of the number of states, we can access the limit r {\textrightarrow} 1 corresponding to correlated percolation, and show that the critical properties of Potts spin clusters cannot in general be obtained from those of Fortuin-Kasteleyn clusters by analytical continuation.}, doi = {10.1088/1742-5468/aca901}, url = {https://iopscience.iop.org/article/10.1088/1742-5468/aca901}, author = {Noel Lamsen and Youness Diouane and Gesualdo Delfino} } @inproceedings {624, title = {Effects of interparticle interaction on the spin transport in a half-filled open elastic Fermi-Hubbard optical lattice}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-1F-05}, address = {Siargao}, abstract = {Spin is a particle property whose study of transport receives attention due to lossless transfer of information. In this study, spin transport is dependent on interparticle interactions in a one-dimensional half-filled open elastic Fermi-Hubbard optical lattice. Near absolute zero temperature temperature, spins flow in the repulsive regime and are not transported in the attractive regime. In addition, as the temperature approaches zero, the abrupt increase of the conductivity for the repulsive regime and the decrease to zero of the conductivity for the attractive regime take place at relatively higher temperatures.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-1F-05}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @inproceedings {626, title = {Election opinion dynamics through the 2D Ising model}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PB-45}, address = {Siargao}, abstract = {The Ising model and its variations have seen regular applications in describing the behavior of systems with many interacting bodies of varying complexity. We explored a zero-field Ising model that includes next nearest neighbor interactions with strength J$_{2}$ to investigate the opinion dynamics of a voting population in a two-party election. We constructed lattices filled with voters preferring to vote for either x candidate or x{\textquoteright} candidate in random configurations. We then allowed these sites to switch preferences using the Metropolis algorithm while varying the influence strength J$_{2}$, of the "clique" of each voter. Our work demonstrates that, when exposing the voting population to biased information/disinformation, increasing J$_{2}$ leads to a decrease in the critical bias of the voters where the overall "alignment" of their voting preferences drops to zero. We also investigated how this introduction of next nearest neighbor interactions is affected by changes in voting population size. Here, we found out that the rate of change at which the critical bias decreases is reduced as the population becomes larger due to the sheer amount of voters inhibiting long-range order among them.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PB-45}, author = {Jose Antonio R. Gamboa and Cristine D. Villagonzalo} } @inproceedings {628, title = {Electronic structure and relative permittivity of α-alumina in the generalized gradient approximation}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PA-05}, address = {Siargao}, abstract = {Pristine α-alumina or α-Al$_{2}$O$_{3}$ is a wide band gap insulator with notable hardness and clarity that make it a prime material for a range of optical and commercial applications. We present first principles calculations of the electronic and optical properties of α-alumina in the generalized gradient approximation. While our results match those of other studies using similar approximations, these computations yield systematically smaller band gaps than observed in experiments. Consequently, the predicted absorption spectrum is redshifted and the refractive index is overestimated. This study serves as a benchmark for future work involving more sophisticated hybrid exchange-correlation functionals that are needed to accurately describe how dilute substitutional defects can form narrow transmission bands in the visible spectrum.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PA-05}, author = {Brongcano, Mark G. and Francis N. C. Paraan} } @conference {645, title = {Enhanced efficiency of a quantum Otto engine based on an XX spin chain near its dynamical phase transition}, year = {2023}, month = {6{\textendash}10 Nov 2023}, pages = {P.26}, publisher = {Asian Network School and Workshop on Complex Condensed Matter Systems 2023}, address = {IOP VAST, Vietnam}, abstract = {Implementation of heat engines in the nanoscale must consider quantum effects. In this study, a quantum Otto engine with an XX spin chain as a working substance was investigated near its dynamical phase transition for its efficiency enhancement. We used two isothermal and two isomagnetic branches for the thermodynamic cycle of the quantum Otto engine. The working substance was operated at the ground state and at a thermal state. The isothermal branches were implemented at zero temperature and inverse temperature βJ >= 1, while the isomagnetic branches at constant |λ/J| < 2. The quantum heat engine was found to achieve a 100\% peak efficiency near the ground state curve in the chemical potential diagram and operates at constant 100\% efficiency for extended regions when the system undergoes dynamical phase transition.}, url = {https://iop.vast.vn/asian/2023/program.php?t=1\&n=26}, author = {Geronimo Allan Jerome Acosta and Cristine D. Villagonzalo} } @article {587, title = {Entanglement entropy distinguishes PT-symmetry and topological phases in a class of non-unitary quantum walks}, journal = {Quantum Inf. Process.}, volume = {22}, year = {2023}, pages = {106}, abstract = {We calculate the hybrid entanglement entropy between coin and walker degrees of freedom in a non-unitary quantum walk. The model possesses a joint parity and time-reversal symmetry or PT-symmetry and supports topological phases when this symmetry is unbroken by its eigenstates. An asymptotic analysis at long times reveals that the quantum walk can indefinitely sustain hybrid entanglement in the unbroken symmetry phase even when gain and loss mechanisms are present. However, when the gain-loss strength is too large, the PT-symmetry of the model is spontaneously broken and entanglement vanishes. The entanglement entropy is therefore an effective and robust parameter for constructing PT-symmetry and topological phase diagrams in this non-unitary dynamical system.}, doi = {10.1007/s11128-023-03848-y}, url = {https://doi.org/10.1007/s11128-023-03848-y}, author = {Gene M. M. Itable and Francis N. C. Paraan} } @inproceedings {625, title = {Entropy and specific heat features of a four spin system at its energy level crossings}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PA-33}, address = {Siargao}, abstract = {A previous study showed that the efficiency of a quantum heat engine utilizing the Lipkin-Meshkov-Glick (LMG) spin system can reach the Carnot limit at low temperatures when the external field reaches the energy level cross points of the ground states. These points occur when different energy levels become degenerate. To delve more into the quantum behavior at the crossing points, this work considered the thermodynamic characteristics of an LMG model consisting of four spins. Using the eigenenergies for the N = 4 spin system with anisotropy, the entropy, and specific heat were numerically obtained in the canonical ensemble and studied as a function of its energy level crossings. It is found that lower values of energy level crossings correspond to more stable entropies and higher specific heat values of the system. These features make the LMG spin system suitable as a working substance in heat engine applications.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PA-33}, author = {Andrei Espencer M. Ordonio and Cristine D. Villagonzalo} } @inproceedings {631, title = {Excitation transfer rates in a cyanobacterial photosystem I in the dipolar coupling approximation}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PB-15}, address = {Siargao}, abstract = {Photosystems are light-harvesting units utilized by photosynthetic organisms. The arrangement of chlorophylls (Chl) in each photosystem varies from organism to organism and is fine-tuned by evolution. In this paper, we study the pathways of excitation transfer in a cyanobacterial photosystem I (Synechococcus elongatus) using an effective Hamiltonian based on F{\"o}rster theory of resonance energy transfer. The off-diagonal terms of the Hamiltonian matrix were calculated in the dipolar coupling approximation to obtain excitation transfer rates between Chl pairs in the network. From these rates, it was found that there is a four-fold preferential excitation flow from the peripheral antenna to the B39 Chl compared to A40. The transfer rate discrepancy can be attributed to the difference in the dipole moment orientations and the spatial locations of the central Mg atom of the Chls. Strongly coupled antenna Chls were identified based on a threshold on the maximum transfer rates.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PB-15}, author = {Ron Michael V. Acda and Francis N. C. Paraan} } @inproceedings {630, title = {Filipino text classification by Universal Language Model Fine-tuning (ULMFiT)}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PB-06}, address = {Siargao}, abstract = {One of the major obstacles in natural language processing is the scarcity of labeled data for some languages. To tackle this issue, transfer learning techniques like Universal Language Model Fine-tuning (ULMFiT) have emerged as effective solutions. This research paper explores the utilization of ULMFiT for addressing text classification challenges in the Filipino language. We follow the ULMFiT approach, involving pretraining a language model, fine-tuning it, and developing a text classifier. We independently reproduce previous results for a binary text classification task on a dataset of text in Filipino. Additionally, we demonstrate the promising performance of the ULMFiT model on a multi-label classification task, achieving hamming losses as low as ~0.10, which are comparable to previous benchmark results obtained with transformer models.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PB-06}, author = {Mary June A. Rica{\~n}a and Francis N. C. Paraan} } @inproceedings {622, title = {First-principles investigation of the electronic and magnetic properties of heptauthrene nanostructure on Cu(111) substrate}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-2F-02}, address = {Siargao}, abstract = {Diradical π-conjugated hydrocarbons have gained research interest due to their predicted high-spin states that make them potential candidates for molecular spintronics applications. Heptauthrene, a phenalenyl diradical with high chemical reactivity, has been recently synthesized on Au(111). However, studies on the physical properties of heptauthrene on substrates are still limited due to its high chemical reactivity and difficulty to synthesize. Here, we use first-principles calculations to investigate the electronic and magnetic properties of heptauthrene in freestanding and Cu(111) substrate-supported systems. Our results show ferromagnetic edge states in freestanding heptauthrene that can be suppressed by the Cu(111) substrate. The results of the study suggest the substrate-controlled spin tunability of heptauthrene and it also serves as a guide in the synthesis of heptauthrene molecules for spintronics and quantum technology applications.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-2F-02}, author = {Gennevieve M. Macam and Feng-Chuan Chuang} } @inproceedings {629, title = {Forecasting next day wildfires through image segmentation using convolutional neural networks}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PB-02}, address = {Siargao}, abstract = {In this study, we trained a convolutional neural network based on the UNET architecture to predict the locations of wildfires on the next day through image segmentation. The Residual UNET does this by generating wildfire predictors from the inputs using feature extraction. The open-source dataset we used was curated for predicting next day wildfires and contains remotely sensed images of 12 input features relevant to the task. We train the models using focal Tversky, weighted cross entropy, and dice loss functions and then compared their performance using dice coefficient, recall, and precision. Analyzing the predicted fire masks showed that the Residual UNET models are able to predict the general locations of next day wildfires.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PB-02}, author = {Joshua Deiondre T. Malalad and Francis N. C. Paraan} } @inproceedings {621, title = {Fractal dimension, critical exponents, and weak universality on a modified 2D Ising model}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-PA-07}, address = {Siargao}, abstract = {We investigate the behavior of a 2D square Ising system with central regions without spins, providing insights into its critical behavior and dimensionality. Increasing the density of these regions changes the dimensionality of the finite lattice, and the critical temperature decreases as the blocked region density increases, consistent with a similar percolation study in 2D. The fractal dimension tends towards D = 1 as the density of blocked sites increases, indicating a more one-dimensional lattice system. Results from the analysis of modified Ising system, where the value of β varies with the degree of dilution or the density of blocked region, ρ, supports the weak universality hypothesis.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-PA-07}, author = {Kryss C. Urbano and Ronald S. Banzon} } @article {649, title = {Magnetocaloric and electrocaloric heat engine and refrigeration cycles in the open Fermi-Hubbard optical dimer with attractive interactions}, journal = {Phys. Lett. A}, volume = {481}, year = {2023}, pages = {129011}, abstract = {Quantum heat engines and refrigerators can be realized in a Fermi-Hubbard optical dimer through immersion in a mean-field Fermi gas bath using the magnetocaloric and electrocaloric effects. It is demonstrated that in the presence of onsite and heat bath-induced attractive interactions, singlet-to-triplet transitions are achieved with a finite external magnetic field. Similarly, triplet-to-singlet transitions occur in the presence of an applied finite electric field. Results show that to lift the degeneracies, considerable electric potential magnitudes are needed. These magnitudes are greater than the magnetic potential strengths where the degeneracies occur. Furthermore, in the attractive regime, combinations of direct and inverse caloric effects can be combined to operate quantum heat engines and refrigerators, like what happens in the repulsive regime.}, doi = {10.1016/j.physleta.2023.129011}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0375960123003912}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @conference {647, title = {Network modeling of chlorophyll excitation transfer rates in cyanobacterial photosystem I in the dipolar coupling approximation}, year = {2023}, month = {28{\textendash}29 Nov 2023}, pages = {BCB-21}, publisher = {50th Philippine Society of Biochemistry and Molecular Biology Annual Convention}, address = {The Manila Hotel}, abstract = {The flow of excitation energy in photosystems can be described by the energy funnel model, where excitations from the higher-energy antenna pigments are funneled toward the lower-energy reaction-center chlorophylls, eventually reaching the P700 where charge separation takes place. Thus, energy transfer flow between chlorophylls in a photosystem can be modeled as a network. In this study, a network of the energy flow between individual chlorophyll nodes in cyanobacterial photosystem I (from Synechococcus elongatus) is constructed. The nodes of the graph are the chlorophyll molecules, which are all the chlorophyll a type. The edge weights are the quantum-mechanical transfer rates constructed under the F{\"o}rster dipole-dipole approximation. From the network, chlorophylls serving as excitation sinks and sources, as well as "central" chlorophylls from a betweenness-centrality-based metric of antenna-to-P700 energy flow, were identified. Characterization of these crucial nodes can be extended to other complex photosynthetic units, as these nodes could play a critical role in the network functioning of photosynthetic energy transfer.}, url = {https://drive.google.com/file/d/1c-k4kQO_Kzfsv_8d_wC6VfCCOBoFXJiu/view}, author = {Ron Michael V. Acda and Francis N. C. Paraan} } @article {650, title = {Prediction of quantum spin Hall and Rashba effects in two-dimensional ilmenite oxides}, journal = {Chinese J. Phys.}, volume = {86}, year = {2023}, pages = {242}, abstract = {Using first-principles calculations, we investigate the structural, electronic, and topological properties of two-dimensional (2D) pristine ilmenite oxides ABO$_{3}$ (A~=~Au, Ag, or Cu; and B~=~Bi, Sb, or As) and their corresponding Janus structures. Phonon dispersions reveal the dynamic stability of these compounds. Interestingly, pristine CuBiO$_{3}$ and AuBiO$_{3}$, and Janus Cu$_{0}$.$_{5}$Ag$_{0}$.$_{5}$BiO$_{3}$, Au$_{0}$.$_{5}$Cu$_{0}$.$_{5}$BiO$_{3}$, Au$_{0}$.$_{5}$Ag$_{0}$.$_{5}$BiO$_{3}$, and CuBi$_{0}$.$_{5}$As$_{0}$.$_{5}$O$_{3}$ are topological insulators, while AuBi$_{0}$.$_{5}$As$_{0}$.$_{5}$O$_{3}$, CuBi$_{0}$.$_{5}$Sb$_{0}$.$_{5}$O$_{3}$, and AuBi$_{0}$.$_{5}$Sb$_{0}$.$_{5}$O$_{3}$ are topological semimetals, as confirmed by their Z2 invariance and conducting edge states under the hybrid functional approach. Moreover, we found van Hove singularities in Au$_{0}$.$_{5}$Ag$_{0}$.$_{5}$BiO$_{3}$ and Cu$_{0}$.$_{5}$Ag$_{0}$.$_{5}$BiO$_{3}$ near the Fermi level, suggesting the coexistence of superconductivity and nontrivial topology. Finally, isotropic Rashba spin-splitting is studied in detail for Au$_{0}$.$_{5}$Ag$_{0}$.$_{5}$BiO$_{3}$. Our findings demonstrate that 2D ilmenite oxides can be a new material playground for potential spintronic applications.}, doi = {10.1016/j.cjph.2023.09.022}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0577907323001806}, author = {Susaiammal Arokiasamy and Gennevieve M. Macam and Rovi Angelo B. Villaos and Aniceto B. Maghirang and Zhi-Quan Huang and Chia-Hsiu Hsu and Guoqing Chang and Feng-Chuan Chuang} } @inproceedings {623, title = {Quantum heat engine efficiency of a small spin system with anisotropy}, booktitle = {Proceedings of the 41st Samahang Pisika ng Pilipinas Physics Conference}, year = {2023}, month = {19{\textendash}21 July 2023}, pages = {SPP-2023-3H-05}, address = {Siargao}, abstract = {The rise of electronic devices lower than the nanoscale shifts the focus to quantum heat engines as they have improved features than their classical counterparts. In this work, the two-spin and three-spin systems using the Lipkin-Meshkov-Glick (LMG) model as the working substance of the heat engine are considered. The efficiency of the quantum heat engine comprised of two reversible isothermal processes and two isomagnetic processes with varying spin anisotropy is investigated. The configuration with the highest anisotropy was found to yield the highest efficiency for the two-spin system, and the most isotropic case was the most efficient for the three-spin system. This is attributed to the effect of anisotropy on the energy levels of the LMG spin system.}, url = {https://proceedings.spp-online.org/article/view/SPP-2023-3H-05}, author = {Gene Michael P. Herman and Cristine D. Villagonzalo} } @article {661, title = {On the RPᴺ$^{-}${\textonesuperior} and CPᴺ$^{-}${\textonesuperior} universality classes}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2023}, year = {2023}, pages = {043204}, abstract = {We recently determined the exact fixed point equations and the spaces of solutions of the two-dimensional RPᴺ$^{-}${\textonesuperior} and CPᴺ$^{-}${\textonesuperior} models using scale invariant scattering theory. Here, we discuss subtleties hidden in some solutions and related to the difference between ferromagnetic and antiferromagnetic interaction.}, doi = {10.1088/1742-5468/acc8c9}, url = {https://iopscience.iop.org/article/10.1088/1742-5468/acc8c9}, author = {Youness Diouane and Noel Lamsen and Gesualdo Delfino} } @conference {646, title = {Topological phases in the ordered double transition metal carbide MXenes}, year = {2023}, month = {6{\textendash}10 Nov 2023}, pages = {P.37}, publisher = {Asian Network School and Workshop on Complex Condensed Matter Systems 2023}, address = {IOP VAST, Vietnam}, abstract = {In this poster, I will discuss the results of our study on two-dimensional MXenes which are materials that continue to gain prominence in research due to their diverse possibilities in chemical composition and surface functionals. We investigated a family of ordered double transition metal MXenes (W$_{2}$M$_{2}$C$_{3}$T$_{2}$, M = Nb, Ta, or V; T = O or F) using first-principles calculations. We found four MXenes with nontrivial topological phases, W$_{2}$Ta$_{2}$C$_{3}$O$_{2}$, W$_{2}$Nb$_{2}$C$_{3}$O$_{2}$, W$_{2}$V$_{2}$C$_{3}$O$_{2}$, and W$_{2}$V$_{2}$C$_{3}$F$_{2}$. Further analysis shows that the the main contributors in the low energy physics of W$_{2}$M$_{2}$C$_{3}$T$_{2}$ are the d orbitals of W and M atoms. The results of the study provides potential candidates of topological materials for experimental realization and spintronic device applications.}, author = {Gennevieve M. Macam and Feng-Chuan Chuang} } @article {577, title = {Caloric effects in an open Fermi{\textendash}Hubbard optical dimer due to onsite and heat bath-induced two-particle interactions}, journal = {J. Magn. Magn. Mater.}, volume = {564}, year = {2022}, pages = {170094}, abstract = {The immersion of the Fermi{\textendash}Hubbard optical dimer in a mean field Fermi gas, acting as a heat bath, modifies the behavior of the statistical mechanical properties of the particles trapped in it. This is done by varying the two-particle interactions induced by the heat bath and the onsite two-particle interaction U. It is shown that in the presence of the heat bath-induced interaction, the partition function Z drops to a minimum finite value in the repulsive regime of U at the normalized temperature region kTt/2, where t is the tunneling parameter. In this temperature region, the convergence points of the respective isolines of the entropy S and the heat capacity Cᵥ move towards each other. Such shift in their features finetune S and Cᵥ relative to their behavior in the absence of two-particle interactions with the bath.}, doi = {10.1016/j.jmmm.2022.170094}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @inproceedings {583, title = {Chemical potential-induced effects on caloric properties of a Fermi-Hubbard dimer}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-1G-04}, address = {Legazpi City}, abstract = {Chemical potential is one of the tunable properties of an optical lattice system when its temperature is varied. In this study, the effects of the chemical potential on the entropy and the heat capacity of a Fermi-Hubbard dimer immersed in a mean-field Fermi gas bath are calculated. Repulsive two-particle interactions are found to require lesser chemical potentials to observe a rapid increase in the entropy at low temperatures. Such phenomena signify quantum level crossings. Furthermore, half-filling of the optical dimer is unnecessary for such phenomena to occur.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-1G-04}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @article {659, title = {Critical points in the CPᴺ$^{-}${\textonesuperior} model}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2022}, year = {2022}, pages = {023201}, abstract = {We use scale invariant scattering theory to obtain the exact equations determining the renormalization group fixed points of the two-dimensional CPᴺ$^{-}${\textonesuperior} model, for N real. Also due to special degeneracies at N = 2 and 3, the space of solutions for N >= 2 reduces to that of the O(N{\texttwosuperior} - 1) model, and accounts for a zero temperature critical point. For N < 2 the space of solutions becomes larger than that of the O(N{\texttwosuperior} - 1) model, with the appearance of new branches of fixed points relevant for criticality in gases of intersecting loops.}, doi = {10.1088/1742-5468/ac4983}, url = {https://iopscience.iop.org/article/10.1088/1742-5468/ac4983}, author = {Youness Diouane and Noel Lamsen and Gesualdo Delfino} } @inproceedings {581, title = {Crossing and anti-crossing of the Lipkin-Meshkov-Glick model for N = 4 spin system}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-2G-06}, address = {Legazpi City}, abstract = {Energy level crossings are degeneracies of two or more energy levels which occur when two levels coincide due to the tuning of an external parameter. In this work, we observe the "motion" of the energy levels in terms of the applied external magnetic field and anisotropy. We demonstrate how the eigenenergies of the anisotropic Lipkin-Meshkov-Glick (LMG) model for the N = 4 spin system shift as a function of the aforementioned parameters. The resulting plots show multiple level crossings as the system becomes isotropic where the LMG model has degenerate ground states along the critical lines determined by the anisotropy parameter. This work has also verified that for the isotropic case, energy level crossings occur exactly at the critical points.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-2G-06}, author = {Andrei Espencer M. Ordonio and Klarence Anne M. Feri and Cristine D. Villagonzalo} } @inproceedings {584, title = {Effective Hamiltonian for a non-unitary quantum walk}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-PB-10}, address = {Legazpi City}, abstract = {We construct an effective Hamiltonian for the non-unitary evolution operator of a multi-step quantum walk with a mechanism for gain and loss. This Hamiltonian is expressed in the basis of the identity and Pauli operators to make its spectrum easy to calculate and its symmetries evident. The parametrization we use allows for an efficient evaluation of the phase boundary where the PT-symmetry of the model is known to be spontaneously broken and shows that the effective Hamiltonian, although non-Hermitian, is real.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-PB-10}, author = {Francis N. C. Paraan and Sven T. Sorupia and Gene M. M. Itable} } @article {603, title = {Electronic and topological band evolution of VB-group transitionmetal monocarbides M$_{2}$C (M=V, Nb, or Ta) bulk and monolayer}, journal = {Mater. Today Commun.}, volume = {32}, year = {2022}, pages = {103875}, abstract = {Two-dimensional transition metal monocarbides (2D MXenes) have attracted intense interest due to their versatility, predicted topological phase, and immense applications. In this study, we investigated the electronic and topological band evolutions of both the bulk and monolayer MXenes, M$_{2}$C (M~= V, Nb, or Ta), using first-principles calculations. Our study shows that all the three bulk M$_{2}$C are semi-metallic and host topological phases. Interestingly, our study showed pristine monolayers V$_{2}$C and Nb$_{2}$C exhibit non-trivial topological phases, while Ta$_{2}$C exhibits trivial phase. Unlike other MXenes, monolayer V$_{2}$C and Nb$_{2}$C host the quantum spin Hall effect without functionalizations. Furthermore, thickness-dependent calculations intriguingly show Lifshitz electronic transition from semi-metallic to topological insulating phase in V$_{2}$C from bilayer to monolayer with a sufficiently large bandgap of 0.32~eV. Moreover, the topological phase transition between the TI state and the trivial state in V$_{2}$C is driven by quantum size effects as the Z$_{2}$ topological invariant notably oscillates between 1 and 0 with varying thickness. Finally, our study demonstrated that VB MXenes could be promising topological materials for spintronics applications.}, keywords = {Electronic structures, First-principles calculations, Mono-transition metal MXenes, Topological insulators, Topological phase transition, Transition metal monocarbides}, doi = {10.1016/j.mtcomm.2022.103875}, author = {Ali Sufyan and Aniceto B. Maghirang and Gennevieve Macam and Zhi-Quan Huang and Chia-Hsiu Hsu and Feng-Chuan Chuang} } @inproceedings {585, title = {Exploring quantum phenomena of various fermionic quantum models through their thermodynamic properties}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-INV-1A-01}, address = {Legazpi City}, abstract = {Thermodynamic properties are usually associated with the macroscopic or bulk properties of a system. In the nanoscale of condensed fermionic systems, their thermodynamics properties such as the thermoelectric coefficient, thermal conductivity or heat capacity, among others, can be used to probe quantum phenomena. Different theoretical models for fermions that have a distinct feature, such as (i) disorder, (ii) two-particle interaction, or (iii) spin-orbit coupling, are explored at low temperature to show how a temperature gradient affects their thermodynamics properties. In turn, these offer insight into the quantum nature of systems described by these fermionic models.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-INV-1A-01}, author = {Cristine Villagonzalo} } @inproceedings {580, title = {Fractal dimension in a modified 2D Ising system with regions without spin}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-PB-09}, address = {Legazpi City}, abstract = {We investigate the change in dimensionality of an Ising system by increasing the area of a central region without spin, essentially decreasing the density of sites with spin. We describe this change by analyzing the geometrical phase transition and change in magnetization as the system changes. We estimate the critical temperature for each lattice with blocked region density ρ and found that the critical temperature decreases as the blocked region density increases suggesting that the reduced dimensionality affects the critical behavior for each ρ. Fractal dimension is also measured by determining the cluster size and radius of gyration and using their power-law relation to estimate its value. It is found that general trend of the plot tends towards D = 1 as the density of blocked sites ρ increases, indicating that the dimension is becoming more one-dimensional.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-PB-09}, author = {Kryss C. Urbano and Ronald S. Banzon} } @article {602, title = {Interplay between anisotropic spin texture and large gap topological insulating phases in functionalized MXenes}, journal = {Chinese J. Phys.}, volume = {77}, year = {2022}, pages = {2346}, abstract = {Massive attention has been given to two-dimensional (2D) MXenes due to their predicted topological phase and promising diverse applications. Using first-principles with hybrid functional calculations, we systematically conducted an extensive study on M$_{2}$C (M~=~Mo, or W) in 1T and 2H structures with various surface terminations T$_{2}$ (T~=~H, O, OH, F, Cl, Br, or I). Pristine Mo$_{2}$C and W$_{2}$C compounds are in the 2H phase. Upon functionalization of H, O, OH and F, they retain the 2H structure, whereas Cl, Br, and I functionalization, the structures transform to 1T phase. Notably, M$_{2}$CO$_{2}$ are found to be 2D topological insulators (TIs) with sizable nontrivial bandgaps as large as 666~meV. Interestingly, 2H M$_{2}$CO$_{2}$ exhibits not only large-gapped Zeeman-type spin splitting at K-point but also anisotropic Rashba spin splitting at Γ-point. The successful synthesis of pristine Mo$_{2}$C and our theoretical study pave a path for future applications of MXene-based 2D TIs.}, doi = {10.1016/j.cjph.2022.04.012}, author = {Aniceto B. Maghirang and Gennevieve Macam and Ali Sufyan and Zhi-Quan Huang and Chia-Hsiu Hsu and Feng-Chuan Chuang} } @inproceedings {582, title = {Quantum Carnot heat engine with an effective external electric field perturbation}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-1D-03}, address = {Legazpi City}, abstract = {The classical approach to heat engines is not enough to study devices in the atomic scale as it utilizes spin-systems as working substances whose behavior is dictated by quantum mechanics. We constructed a quantum heat engine that follows the Carnot cycle with two reversible isothermal and isomagnetic processes in contact with heat baths of two different temperatures, based on the Lipkin-Meshkov-Glick (LMG) model. The engine runs between two magnetic fields with one kept constant and the other magnetic field varied. A perturbation in the form of an effective external electric field in the x-direction, δJx, was introduced to the system where δ << 1. Up to the second-order energy correction was determined using the time-independent perturbation theory and the unperturbed LMG eigenstates as basis. The entropy, internal energy, and the work done in each cycle were determined and used to obtain the efficiency of the system with spins N = 2. For a fixed set of values for the high-temperature heat bath and the low-temperature heat bath, this work demonstrates that the system{\textquoteright}s efficiency is dependent on δ and the varying magnetic field. The system{\textquoteright}s maximum efficiency was found to approach the value of the Carnot limit.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-1D-03}, author = {Gene Michael P. Herman and Cristine D. Villagonzalo} } @article {574, title = {Refrigeration using magnetocaloric and electrocaloric effects in a Fermi-Hubbard optical dimer exposed to a heat bath}, journal = {Physica A}, volume = {600}, year = {2022}, pages = {127540}, abstract = {We consider a Fermi{\textendash}Hubbard dimer exposed to external electromagnetic fields and a Fermi gas bath under the assumptions of a repulsive two-particle interaction and the half-filling condition. Using the exact diagonalization method, it was found that the entropy and heat capacity rapidly rise within distinct localized regions of the magnetic and electric fields at low temperatures. The behavior of the magnetic (electric) Gr{\"u}neisen ratio denotes that the direction of the external field determines the magnetization or demagnetization (polarization or depolarization) due to the magnetocaloric (electrocaloric) effect among the lattice particles at a given temperature. At the same time, the isothermal entropic change as a function of the temperature indicates that refrigeration is optimized when the electric field along the line joining the two sites of the optical lattice is assisted by a transverse magnetic field.}, doi = {10.1016/j.physa.2022.127540}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @article {601, title = {Robust tunable large-gap quantum spin Hall states in monolayer Cu$_{2}$S on insulating substrates}, journal = {ACS Omega}, volume = {7}, year = {2022}, pages = {15760}, abstract = {Quantum spin Hall (QSH) insulators with large band gaps and dissipationless edge states are of both technological and scientific interest. Although numerous two-dimensional (2D) systems have been predicted to host the QSH phase, very few of them harbor large band gaps and retain their nontrivial band topology when they are deposited on substrates. Here, based on a first-principles analysis with hybrid functional calculations, we investigated the electronic and topological properties of inversion-asymmetric monolayer copper sulfide (Cu$_{2}$S). Interestingly, we found that monolayer Cu$_{2}$S possesses an intrinsic QSH phase, Rashba spin splitting, and a large band gap of 220 meV that is suitable for room-temperature applications. Most importantly, we constructed heterostructures of a Cu$_{2}$S film on PtTe$_{2}$, h-BN, and Cu(111) substrates and found that the topological properties remain preserved upon an interface with these substrates. Our findings suggest Cu$_{2}$S as a possible platform to realize inversion-asymmetric QSH insulators with potential applications in low-dissipation electronic devices.}, doi = {10.1021/acsomega.2c00781}, author = {Ali Sufyan and Gennevieve Macam and Zhi-Quan Huang and Chia-Hsiu Hsu and Feng-Chuan Chuang} } @conference {593, title = {Spin transport in a Fermi-Hubbard optical lattice interacting with a Fermi gas bath}, year = {2022}, month = {18{\textendash}24 Aug 2022}, pages = {P23-SF4-07}, publisher = {29th International Conference on Low Temperature Physics}, address = {Presented online}, url = {https://www.lt29.jp/}, author = {Vladimir P. Villegas and Cristine D. Villagonzalo} } @article {600, title = {Spin-lattice-charge coupling in quasi-one-dimensional spin-chain NiTe$_{2}$O$_{5}$}, journal = {Phys. Rev. Mater.}, volume = {6}, year = {2022}, pages = {044409}, abstract = {A high-quality NiTe$_{2}$O$_{5}$ single crystal was grown via the flux method and characterized using synchrotron x-ray diffraction (XRD) and electron probe microscopy techniques. The dc magnetization (M) confirms the antiferromagnetic long-range ordering temperature (TN) at 28.5 K. An apparent domelike dielectric anomaly near TN, with scaling of magnetodielectric (MD) coupling with magnetization (MD\% ∝ M{\texttwosuperior}), signifies higher-order magnetoelectric (ME) coupling. The critical finding is that magnetoelastic coupling plays a pivotal role in bridging the electrical and magnetic dipoles, which was further confirmed by temperature-dependent XRD. In addition, the theoretical charge density difference maps indicate that the emergence of electrical dipoles between the Ni and O atoms below TN originates through p-d hybridization. Thus, the p-d hybridization-induced magnetoelastic coupling is considered a possible mechanism for the higher-order ME effect in this quasi-onedimensional spin-chain NiTe$_{2}$O$_{5}$.}, doi = {10.1103/PhysRevMaterials.6.044409}, author = {Ajay Tiwari and D. Chandrasekhar Kakarla and Gennevieve Macam and Chia-Hsiu Hsu and Feng-Chuan Chuang and H. C. Wu and T. W. Kuo and Arkadeb Pal and H. Chou and D. P. Gulo and H. L. Liu and Y. C. Chuang and Y. C. Lai and C. A. Lee and Mitch M. C. Chou and H. D. Yang} } @inproceedings {615, title = {Topological phases in the ordered double transition metal carbide MXenes (W$_{2}$M$_{2}$C$_{3}$T$_{2}$, M = Nb, Ta, or V; T = O or F)}, booktitle = {Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference}, year = {2022}, month = {19{\textendash}21 Oct 2022}, pages = {SPP-2022-3E-02}, address = {Legazpi City}, abstract = {Two-dimensional MXenes continue to gain prominence in research due to their diverse possibilities in chemical composition and surface functionals which could lead to a variety of applications. Here, we investigate the ordered double transition metal MXenes (W$_{2}$M$_{2}$C$_{3}$T$_{2}$, M = Nb, Ta, or V; T = O or F) using first-principles calculations. We predict four MXenes, (W$_{2}$Ta$_{2}$C$_{3}$O$_{2}$, W$_{2}$Nb$_{2}$C$_{3}$O$_{2}$, W$_{2}$V$_{2}$C$_{3}$O$_{2}$, and W$_{2}$V$_{2}$C$_{3}$F$_{2}$ to exhibit nontrivial topological phases. Orbital analysis shows that the d orbitals of W and M atoms are the main contributors in the low energy physics of W$_{2}$M$_{2}$C$_{3}$T$_{2}$. The results of the study provides potential candidates of topological materials for experimental realization and spintronics application.}, url = {https://proceedings.spp-online.org/article/view/SPP-2022-3E-02}, author = {Gennevieve M. Macam and Feng-Chuan Chuang} } @article {604, title = {Band engineering and van Hove singularity on HfX$_{2}$ thin films (X = S, Se, or Te)}, journal = {ACS Appl. Electron. Mater.}, volume = {3}, year = {2021}, pages = {1071}, abstract = {Two-dimensional transition metal dichalcogenides (TMDs) have become well-known due to their versatile and tunable physical properties for potential applications, specifically on low-power and optical devices. Here, we explored the structural stability and electronic properties of bulk and thin-film (from 1 up to 6 layers) structures of hafnium dichalcogenides (HfX$_{2}$, X = S, Se, or Te) using first-principles calculations. Our calculations reveal that the most stable phase is 1T for both thin films and bulk. The bulk and thin-film structures of HfTe$_{2}$ are semimetallic, while those of HfS$_{2}$ and HfSe$_{2}$ are insulating. Both HfS$_{2}$ and HfSe$_{2}$ thin films exhibit a decreasing band gap with increasing thickness, while HfTe$_{2}$ thin films remain semimetallic with increasing number of layers. Moreover, van Hove singularity (vHs), due to the contribution of the pz orbital from S atoms, is observed in 3L-HfS$_{2}$ at the valence band maximum, which can be further enhanced by applying an in-plane biaxial strain, suggesting possible superconductivity. Finally, the bulk and monolayer band structures of HfTe$_{2}$, under HSE06 and GGA + U with the effective Hubbard U parameter of 4.6 eV, are in good agreement with the experimental ARPES data. Our results indeed show that HfX$_{2}$ have sensitive and tunable electronic properties through film thickness control and strain for future potential applications.}, doi = {10.1021/acsaelm.0c00907}, author = {Harvey N. Cruzado and John Symon C. Dizon and Gennevieve M. Macam and Rovi Angelo B. Villaos and Thi My Duyen Huynh and Liang-Ying Feng and Zhi-Quan Huang and Chia-Hsiu Hsu and Shin-Ming Huang and Hsin Lin and Feng-Chuan Chuang} } @inproceedings {villegas2021, title = {Canonical ensemble profile of a Fermi-Hubbard model treated as a double qubit chain}, booktitle = {Proceedings of the 39th Samahang Pisika ng Pilipinas Physics Conference}, year = {2021}, month = {20{\textendash}22 Oct 2021}, pages = {SPP-2021-2B-03}, address = {Presented online}, abstract = {Through the Jordan-Wigner transformation, a Fermi-Hubbard (FH) optical lattice can be mapped onto a double qubit chain system (QS). In this study, the partition function and the Helmholtz free energy were calculated for a FH dimer and a double QS double well. The differences of the values of the two properties as functions of temperature were taken and are shown as saturating to a constant as the temperature increases. This implies that electrons can be emulated as qubits.}, url = {https://proceedings.spp-online.org/article/view/SPP-2021-2B-03}, author = {Vladimir P. Villegas and Cristine Villagonzalo} } @article {658, title = {Critical points in the RPᴺ$^{-}${\textonesuperior} model}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2021}, year = {2021}, pages = {033214}, abstract = {The space of solutions of the exact renormalization group fixed point equations of the two-dimensional RPᴺ$^{-}${\textonesuperior} model, which we recently obtained within the scale invariant scattering framework, is explored for continuous values of N >= 0. Quasi-long-range order occurs only for N = 2, and allows for several lines of fixed points meeting at the Berezinskii-Kosterlitz-Thouless transition point. A rich pattern of fixed points is present below N* = 2.244 21. . , while only zero temperature criticality in the O(N(N + 1)/2 - 1) universality class can occur above this value. The interpretation of an extra solution at N = 3 requires the identification of a path to criticality specific to this value of N.}, doi = {10.1088/1742-5468/abe6fc}, url = {https://iopscience.iop.org/article/10.1088/1742-5468/abe6fc}, author = {Youness Diouane and Noel Lamsen and Gesualdo Delfino} } @inproceedings {delarosa2021, title = {Entanglement detection via quantum Fisher information in an XY dimer}, booktitle = {Proceedings of the 39th Samahang Pisika ng Pilipinas Physics Conference}, year = {2021}, month = {20{\textendash}22 Oct 2021}, pages = {SPP-2021-PA-05}, address = {Presented online}, abstract = {We use an entanglement criterion that is based on the quantum Fisher information to detect entanglement in thermal mixed states of an XY dimer. In the absence of an external magnetic field we find that it detects entanglement only in the anisotropic regions beyond the Ising line. Entanglement is destroyed at high temperatures, and this criterion is only able to detect entanglement at a lower threshold temperature than concurrence.}, url = {https://proceedings.spp-online.org/article/view/SPP-2021-PA-05}, author = {Rafael S. dela Rosa and Apolinario Miguel I. Tan and Francis N. C. Paraan} } @article {566, title = {Optimal fixed-point quantum search in an interacting Ising spin system}, journal = {Quantum Inf. Process.}, volume = {20}, year = {2021}, pages = {90}, abstract = {In Grover{\textquoteright}s search algorithm, a priori knowledge of the number of target states is needed to effectively find a solution. This is due to the inherent oscillatory nature of unitary gates in the algorithm. A fixed-point quantum search is introduced in [Phys. Rev. Lett. 113, 210501 (2014)] to mitigate this oscillation even without knowing the size of the target space. This is done by modifying the phase inversion and oracle of the original Grover{\textquoteright}s algorithm so that the phase can assume intermediate values in [-π,π]. Naturally, qubits in a quantum computer are interacting among themselves and this might introduce an error in the phase assignment. In this work, we used the Ising spin chain to simulate the interactions among the qubits and demonstrate how to implement the fixed-point quantum search. By inspecting the state vectors after some finite number of iterations, we found that the error is primarily due to the phase difference of the ideal target state with that of the final state. Further investigation shows that high fidelity between the ideal and real evolution can be achieved by using a low Rabi frequency.}, doi = {10.1007/s11128-021-03023-1}, author = {Neris I. Sombillo and Ronald S. Banzon and Cristine Villagonzalo} } @article {606, title = {Prediction of massless Dirac fermions in a carbon nitride covalent network}, journal = {Appl. Phys. Lett.}, volume = {118}, year = {2021}, pages = {133104}, abstract = {Two-dimensional (2D) Dirac materials have received tremendous attention due to their potential applications in spintronics and energy applications. Motivated by recent experimental synthesis of a carbon nitride network with a C$_{2}$$_{2}$N$_{4}$ stoichiometry, the N-doped graphdiyne, or pyrazinoquinoxaline-based graphdiyne (PQ-GDY), we studied the electronic and topological properties of the PQ-GDY monolayer using first-principles calculations. Surprisingly, we found that the PQ-GDY monolayer indeed is a 2D Dirac semimetal also known as 2D topologically nontrivial semimetal. The linear band dispersions around the Dirac point are mainly composed of the bonding and antibonding pz-orbitals of C and N atoms. In combination with parity analysis, we found that the mechanism of band inversion in PQ-GDY is similar to the strain-induced Dirac cone in GDY. The underlying physical property of strained GDY is equivalent to expanding the single center benzene into the three benzene rings observed in PQ-GDY. Finally, the formed Dirac cone located on the Y-Γ high-symmetry line is very robust, and a bandgap is opened only after including a large artificial spin{\textendash}orbit coupling, which transforms it to a 2D topological insulator.}, doi = {10.1063/5.0046069}, author = {Jiangming Cao and Zhi-Quan Huang and Gennevieve Macam and Yifan Gao and Naga Venkateswara Rao Nulakani and Xun Ge and Xiang Ye and Feng-Chuan Chuang and Li Huang} } @inproceedings {feri2021, title = {Specific heat behavior in finite-sized Lipkin-Meshkov-Glick spin system}, booktitle = {Proceedings of the 39th Samahang Pisika ng Pilipinas Physics Conference}, year = {2021}, month = {20{\textendash}22 Oct 2021}, pages = {SPP-2021-1F-05}, address = {Presented online}, abstract = {A quantum heat engine whose working substance is described by the Lipkin-Meshkov-Glick (LMG) model has been shown to improve its efficiency when the LMG system is near its quantum phase transition. It is of interest to know how the specific heat of such an engine will behave under similar conditions. Therefore, in this work, we construct the specific heat curves of the LMG spin system consisting of spin-1/2 particles in a plane of sizes N = 2, 4, 6, 8. Effects of the field strength, temperature, and system size on the specific heat are analyzed. Salient features of the specific heat curve as a function of field strength are observed in relation to the ground state degeneracy that occurs in key field strength values.}, url = {https://proceedings.spp-online.org/article/view/SPP-2021-1F-05}, author = {Klarence Anne M. Feri and Cristine Villagonzalo} } @article {605, title = {Theoretical prediction of topological insulators in two-dimensional ternary transition metal chalcogenides (MM{\textquoteright}X$_{4}$, M~=~Ta, Nb, or V; M{\textquoteright}= Ir, Rh, or Co; X~=~Se or Te)}, journal = {Chinese J. Phys.}, volume = {73}, year = {2021}, pages = {95}, abstract = {Ternary transition metal chalcogenides (TTMCs) have attracted interest due to the discovery of their Weyl semimetallic property and the recent synthesis of layered TTMCs which are regarded as potential candidates for two-dimensional (2D) topological insulators. Here, employing first-principles calculations, we predicted the emergence of non-trivial band topologies in the monolayer MM{\textquoteright}X$_{4}$ family (M= V, Nb, or Ta; M{\textquoteright}~=~Co, Rh, or Ir; and X~=~Se or Te) within hybrid functional calculations. Five of eighteen 2D materials were found to be topological insulators, while four of them are magnetic thin films. The nontrivial topologies were verified via the calculated Z$_{2}$ topological invariant and topologically protected edge states. Further calculations showed a strain-induced phase transition in VCoTe$_{4}$ from a magnetic phase to a nonmagnetic topological insulating phase. Our comprehensive study revealed a diverse family of monolayer ternary transition metal chalcogenides adding new members to the current catalog of 2D topological insulators and 2D magnetic materials.}, doi = {10.1016/j.cjph.2021.06.014}, author = {Ali Sufyan and Gennevieve Macam and Chia-Hsiu Hsu and Zhi-Quan Huang and Shin-Ming Huang and Hsin Lin and Feng-Chuan Chuang} } @article {607, title = {Tuning topological phases and electronic properties of monolayer ternary transition metal chalcogenides (ABX$_{4}$, A/B = Zr, Hf, or Ti; X = S, Se, or Te)}, journal = {Appl. Phys. Lett.}, volume = {118}, year = {2021}, pages = {111901}, abstract = {Topological materials are very promising materials for technological applications ranging from spintronics to quantum computation. Here, based on first-principles calculations, we predict a family of two-dimensional (2D) topological materials in nine ternary transition metal chalcogenides (TTMCs) ABX$_{4}$, where A/B = Zr, Hf, or Ti and X = S, Se, or Te. A total of three compounds (ZrTiTe$_{4}$, HfZrTe$_{4}$, and HfTiTe$_{4}$) are identified to be nontrivial within a hybrid functional calculation. The nontrivial phase originated from the p-d band inversion at the Г point with spin-orbit coupling. The structural stability of these monolayers is confirmed by phonon spectrum analysis, showing no negative phonon frequencies. The diversity of TTMCs will open a wide possibility for tuning the bandgap and will provide a variety of opportunities for 2D and topological materials research.}, doi = {10.1063/5.0036838}, author = {Gennevieve Macam and Ali Sufyan and Zhi-Quan Huang and Chia-Hsiu Hsu and Shin-Ming Huang and Hsin Lin and Feng-Chuan Chuang} } @article {657, title = {Absence of nematic quasi-long-range order in two-dimensional liquid crystals with three director components}, journal = {J. Phys. A Math. Theor.}, volume = {54}, year = {2020}, pages = {03LT01}, abstract = {The Lebwohl-Lasher model describes the isotropic-nematic transition in liquid crystals. In two dimensions, where its continuous symmetry cannot break spontaneously, it is investigated numerically since decades to verify, in particular, the conjecture of a topological transition leading to a nematic phase with quasi-long-range order. We use scale invariant scattering theory to exactly determine the renormalization group fixed points in the general case of N director components (RPᴺ$^{-}${\textonesuperior} model), which yields the Lebwohl-Lasher model for N = 3. For N > 2 we show the absence of quasi-long-range order and the presence of a zero temperature critical point in the universality class of the O(N(N + 1)/2 - 1) model. For N = 2 the fixed point equations yield the Berezinskii-Kosterlitz-Thouless transition required by the correspondence RP{\textonesuperior} \~{} O(2).}, doi = {10.1088/1751-8121/abd2fc}, url = {https://iopscience.iop.org/article/10.1088/1751-8121/abd2fc}, author = {Gesualdo Delfino and Youness Diouane and Noel Lamsen} } @inproceedings {548, title = {Age-dependent random deaths by Verhulst factor in an iteroparous Penna model}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-2A-10}, address = {Presented online}, abstract = {An age-dependent Verhulst death factor was implemented using the Penna bit string model. Adaptation is simulated by decreasing the effect of carrying capacity at certain ages. We have shown that the sudden immunity to environmental effects produces population with greater size, higher diversity index, and extended lifespan. Older individuals are able to adapt to the environment.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-2A-10}, author = {Jammy Rey C. Guinid and Ronald S. Banzon} } @inproceedings {547, title = {Characterization and synthesis of classical reversible circuits}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-4A-04}, address = {Presented online}, abstract = {Irreversible circuits were transformed into their equivalent reversible circuits. The resulting reversible circuits were optimized using a synthesis method proposed by Miller, Maslov, and Dueck, and a line reduction algorithm proposed by Wille, Soeken, and Drechsler. The application of the line-reduction algorithm reduced the number of circuit lines from 5 to 4. The effect of the line-reduction algorithm on the matrix representation of the original circuit was shown to preserve the reversibility of the function. It was also shown that only the matrix representation of a circuit or cascade of gates is needed to determine the operation of its n successive applications, which may be useful in length reduction of reversible circuits.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-4A-04}, author = {Joanne Mae B. Adelino and Ronald S. Banzon} } @inproceedings {552, title = {Characterization of phonon density of states of a graphene junction beyond nearest neighbor interactions}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-4G-05}, address = {Presented online}, abstract = {Graphene has exceptional thermal properties that has presented a wide range of applications. Ballistic thermal transport in graphene due to phonons was made possible by placing a zigzag graphene junction in the middle of a heat sink and a heat source- which induced a temperature gradient that caused heat to flow through the junction. Following the harmonic oscillator model for the graphene junction, interlayer and intralayer interactions were derived beyond nearest neighbors. This paper aims to characterize the zigzag graphene junction{\textquoteright}s phonon density of states and examine the effects of adding next nearest neighbors and varying the bond stretching force constant, ks, on the next nearest neighbor interactions. We observed a wider distribution of energies when adding next nearest neighbor interactions at equal ks. Varying ks showed similar results as this indicates the strength of interaction between the next nearest neighboring atoms.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-4G-05}, author = {Krishna Lyn Delima and Cristine Villagonzalo} } @inproceedings {546, title = {Cluster behavior in a finite 2D Ising model with central blocked regions}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-4G-03}, address = {Presented online}, abstract = {We simulate a 2D ferromagnetic Ising model in a square lattice with non-periodic or finite boundary conditions. We implemented the Monte Carlo Metropolis algorithm to simulate the possible spin configurations of a square lattice with a central region without spins. The resulting magnetic domains of the system were investigated under varying sizes of the blocked region and at different temperature points. It was then observed that higher number of clusters, but of smaller cluster size, occur at high temperatures. Meanwhile, the number of positive and negative spins become almost equal beyond the critical temperature, however, no discernible trend could be observed in the spin up and spin down cluster distribution.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-4G-03}, author = {Jersey Dianne T. Ganding and Ronald S. Banzon} } @inproceedings {551, title = {Drude model electron motion in 2D space with applied electric fields}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-4G-04}, address = {Presented online}, abstract = {The key to the research on emergent materials is the investigation of their response to modulated fields. Here in this work, the differential equation for electron motion is solved and plotted using Fortran and gnuplot to analyze the charge-carrier dynamical behavior in two-dimensional (2D) materials through the Drude model. Momentum decay of an electron in motion inside a material is compared with three other cases of applied electric fields. Properties such as speed and current density of the electron are also determined to show how this old model still functions in today{\textquoteright}s science.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-4G-04}, author = {Tim Jeff M. Rodriguez and Cristine Villagonzalo} } @inproceedings {544, title = {Entanglement in a model with power law interactions}, booktitle = {Book of Abstracts of the 22nd Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2020}, month = {24 Oct 2020}, pages = {5}, address = {Presented online}, abstract = {

In this talk we present an exact approach to calculating the entanglement entropy in spin chains that are described by conformal theory at quantum criticality. The method was initially used to study entanglement in free fermions and the XY model, but it turns out that Kitaev chains with long-ranged power law interactions also fall in the same solvable class. We evaluate the Schmidt gap in the entanglement spectrum and use it to map out the phase diagram of the model. Conformal features about the quantum critical line reveal how the universal scaling relations are affected by the power law exponent of the interactions.

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}, author = {Francis N. C. Paraan and Cleofe Dennielle P. Ayang-ang} } @inproceedings {549, title = {Free energy in a spin transport among particles in a Fermi-Hubbard optical lattice}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-5C-03}, address = {Presented online}, abstract = {The Fermi-Hubbard model investigates the dynamics of fermions confined in a one-dimensional (1D) optical lattice. In turn, the lattice is confined to a heat bath consisting of a fermionic quantum gas. Here, we use the path integral method to investigate the effects of the coupling at zero temperature and determine the five processes among bath particles which facilitate spin transport among optical lattice particles. Furthermore, we compute for the free energy per lattice site during such process.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-5C-03}, author = {Vladimir P. Villegas and Cristine Villagonzalo} } @article {609, title = {Giant emission enhancement of solid-state gold nanoclusters by surface engineering}, journal = {Angew. Chem. Int. Ed.}, volume = {59}, year = {2020}, pages = {8270}, abstract = {Abstract Ligand-induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical [Au$_{2}$$_{5}$(SR{\textonesuperior})$_{1}$$_{8}$]$^{-}$ cluster (1) while maintaining its icosahedral Au$_{1}$$_{3}$ core for the synthesis of a new bimetallic [Au$_{1}$$_{9}$Cd$_{3}$(SR{\texttwosuperior})$_{1}$$_{8}$]$^{-}$ cluster (2). Single-crystal X-ray diffraction studies reveal that six bidentate Au$_{2}$(SR{\textonesuperior})$_{3}$ motifs (L2) attached to the Au$_{1}$$_{3}$ core of 1 were replaced by three quadridentate Au$_{2}$Cd(SR{\texttwosuperior})$_{6}$ motifs (L4) to create a bimetallic cluster 2. Experimental and theoretical results demonstrate a stronger electronic interaction between the surface motifs (Au$_{2}$Cd(SR{\texttwosuperior})$_{6}$) and the Au$_{1}$$_{3}$ core, attributed to a more compact cluster structure and a larger energy gap of 2 compared to that of 1. These factors dramatically enhance the photoluminescence quantum efficiency and lifetime of crystal of the cluster 2. This work provides a new route for the design of a wide range of bimetallic/alloy metal nanoclusters with superior optoelectronic properties and functionality.}, doi = {10.1002/anie.202001034}, author = {Chuanhao Yao and Cong-Qiao Xu and In-Hyeok Park and Meng Zhao and Ziyu Zhu and Jing Li and Xiao Hai and Hanyan Fang and Yong Zhang and Gennevieve Macam and Jinghua Teng and Lin Li and Qing-Hua Xu and Feng-Chuan Chuang and Junpeng Lu and Chenliang Su and Jun Li and Jiong Lu} } @article {610, title = {Large-gap topological insulators in functionalized ordered double transition metal carbide MXenes}, journal = {Phys. Rev. B}, volume = {102}, year = {2020}, pages = {075306}, abstract = {Two-dimensional MXenes continue to receive much research attention owing to their versatility and predicted topological phase, which are yet to be fully explored. Here, we conduct a rigorous search on M$_{2}${\textquoteright}M{\textquoteright}{\textquoteright}C$_{2}$ (M{\textquoteright} = V , Nb , or Ta ; M{\textquoteright}{\textquoteright} = Ti , Zr , or Hf) with various surface terminations, X$_{2}$ (X = F , Cl , Br , I , O , H , or OH) , using first-principles calculations. The majority of the systems exhibit the topological phase with semimetallic band structures. Most importantly, fluorinated MXenes, M$_{2}${\textquoteright}M{\textquoteright}{\textquoteright}C$_{2}$F$_{2}$, are topological insulators. They possess sizable nontrivial band gaps from 34 to 318 meV using Heyd-Scuseria-Ernzerhof (HSE) hybrid functional calculations which are within the range capable of realizing quantum spin-Hall effects even at room temperature. Furthermore, the d orbitals of M{\textquoteright} and M{\textquoteright}{\textquoteright} atoms mostly contribute to the spin-orbit coupling-induced band gaps. Selecting V$_{2}$TiC$_{2}$F$_{2}$ as an exemplar, we demonstrate the presence of edge states, verifying the calculated Z$_{2}$ invariant, and reveal its robustness against tensile strain. Finally, we propose SiC(0001) as a candidate substrate for material realization as it can preserve the nontrivial band topology.}, doi = {10.1103/PhysRevB.102.075306}, author = {Zhi-Quan Huang and Mei-Ling Xu and Gennevieve Macam and Chia-Hsiu Hsu and Feng-Chuan Chuang} } @article {608, title = {Quantum anomalous Hall insulator phases in Fe-doped GaBi honeycomb}, journal = {Chinese J. Phys.}, volume = {67}, year = {2020}, pages = {246}, abstract = {We discuss electronic and magnetic properties of the Fe-doped GaBi honeycomb using first principles calculations. Our analysis shows that the pristine GaBi honeycomb transitions from being a two-dimensional quantum spin Hall (QSH) insulator to a quantum anomalous Hall (QAH) insulator when it is doped with one Fe atom in a 4 {\texttimes} 4 GaBi honeycomb. The QAH phase in Fe-doped GaBi is found to be robust in that it maintains its Chern number (C = 1) under fairly large strains (\~{} 4\%) and supports a gap as large as 112~meV at 2.21\% strain. The QAH phase is also retained when the Fe-doped GaBi is placed on a CdTe substrate, suggesting that Fe-doped GaBi films could be useful for spintronics applications.}, doi = {10.1016/j.cjph.2020.07.007}, url = {https://www.sciencedirect.com/science/article/pii/S0577907320301866}, author = {Zhi-Quan Huang and Chia-Hsiu Hsu and Christian P. Crisostomo and Gennevieve Macam and Jing-Rong Su and Hsin Lin and Arun Bansil and Feng-Chuan Chuang} } @article {541, title = {Selective capture of CO$_{2}$ over N$_{2}$ and CH$_{4}$: B clusters and their size effects}, journal = {Mater. Today Commun.}, volume = {22}, year = {2020}, pages = {100712}, abstract = {Using density-functional theory (DFT), we investigate the selectivity of adsorption of CO$_{2}$ over N$_{2}$ and CH$_{4}$ on planar-type B clusters, based on our previous finding of strong chemisorption of CO$_{2}$ on the B$_{1}$$_{0}$$_{-}$$_{1}$$_{3}$ planar and quasiplanar clusters. We consider the prototype B$_{8}$ and B$_{1}$$_{2}$ planar-type clusters and perform a comparative study of the adsorption of the three molecules on these clusters. We find that, at room temperature, CO$_{2}$ can be separated from N$_{2}$ by selective binding to the B$_{1}$$_{2}$ cluster and not to the B$_{8}$ cluster. Selective adsorption of CO$_{2}$ over CH$_{4}$ at room temperature is possible for both clusters. Based on our DFT-adsorption data (including also a semi-infinite Boron sheet) and the available literature-adsorption value for N$_{2}$ on the planar-type B$_{3}$$_{6}$ cluster, we discuss the selectivity trend of CO$_{2}$ adsorption over N$_{2}$ and CH$_{4}$ with planar-cluster size, showing that it extends over sizes including B$_{1}$$_{0}$$_{-}$$_{1}$$_{3}$ clusters and significantly larger.}, doi = {10.1016/j.mtcomm.2019.100712}, url = {https://www.sciencedirect.com/science/article/abs/pii/S2352492819305719}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @article {611, title = {Spin-orbit quantum impurity in a topological magnet}, journal = {Nat. Commun.}, volume = {11}, year = {2020}, pages = {4415}, abstract = {Quantum states induced by single-atomic impurities are at the frontier of physics and material science. While such states have been reported in high-temperature superconductors and dilute magnetic semiconductors, they are unexplored in topological magnets which can feature spin-orbit tunability. Here we use spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) to study the engineered quantum impurity in a topological magnet Co$_{3}$Sn$_{2}$S$_{2}$. We find that each substituted In impurity introduces a striking localized bound state. Our systematic magnetization-polarized probe reveals that this bound state is spin-down polarized, in lock with a negative orbital magnetization. Moreover, the magnetic bound states of neighboring impurities interact to form quantized orbitals, exhibiting an intriguing spin-orbit splitting, analogous to the splitting of the topological fermion line. Our work collectively demonstrates the strong spin-orbit effect of the single-atomic impurity at the quantum level, suggesting that a nonmagnetic impurity can introduce spin-orbit coupled magnetic resonance in topological magnets.}, doi = {10.1038/s41467-020-18111-6}, author = {Jia-Xin Yin and Nana Shumiya and Yuxiao Jiang and Huibin Zhou and Gennevieve Macam and Hano Omar Mohammad Sura and Songtian S. Zhang and Zi-Jia Cheng and Zurab Guguchia and Yangmu Li and Qi Wang and Maksim Litskevich and Ilya Belopolski and Xian P. Yang and Tyler A. Cochran and Guoqing Chang and Qi Zhang and Zhi-Quan Huang and Feng-Chuan Chuang and Hsin Lin and Hechang Lei and Brian M. Andersen and Ziqiang Wang and Shuang Ji and M. Zahid Hasan} } @inproceedings {550, title = {Temperature dependence of three-dimensional thermoelectric properties of a free electron gas-like material}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-4G-01}, address = {Presented online}, abstract = {

Regeneration of electricity from waste heat can be done through the use of thermoelectric media. In this work, how the bulk thermoelectric properties vary with temperature were simulated using the Fermi energy for Bi2Te3{\textemdash}a promising material for thermoelectric generators. The numerical calculations were based on the equations derived by J. Muldera in 2006 for a free electron gas in three dimensions. The temperature dependence of the thermoelectric properties, such as the thermoelectric power, thermal conductivity and the figure of merit were determined by keeping the number density of charge carriers constant at their Fermi level value. The results show that such a material with a Bi2Te3 Fermi level has thermoelectric properties suited for room temperature applications.

}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-4G-01}, author = {Jairus Carlo F. Calpatura and Cristine Villagonzalo} } @inproceedings {545, title = {Using YOLOv3 to detect colorectal polyps in video}, booktitle = {Proceedings of the 38th Samahang Pisika ng Pilipinas Physics Conference}, year = {2020}, month = {19{\textendash}23 Oct 2020}, pages = {SPP-2020-2A-05}, address = {Presented online}, abstract = {A model based on the You Only Look Once (YOLO) algorithm was trained to detect polyps on a dataset of 503 polyp-positive images taken from colonoscopy video frames. We achieve precision on test sets that is comparable to the performance of a previously described model trained on a much larger set of 5,545 images. However, our model has a lower recall and missed some polyps in the test set.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2020-2A-05}, author = {Mary Chris R. Go and Francis N. C. Paraan} } @inproceedings {urbanoSPP2019, title = {2D Ising model with regions without spin}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1G-04}, address = {Tagbilaran City, Philippines}, abstract = {The percolation threshold of 2D Ising lattice with a nonmagnetic region was found to change as the ares of this region increases, effectively changing the region with spins from 2D to 1D. These results are found to be consistent with the effective change in dimensionality of the lattice in a previous study that focuses on the change of the system with a critical temperature (2D) to one without (1D).}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1G-04}, author = {Kryss Urbano and Ronald Banzon} } @article {596, title = {Atomically precise bottom-up synthesis of π-extended [5]triangulene}, journal = {Sci. Adv.}, volume = {5}, year = {2019}, pages = {eaav7717}, abstract = {The zigzag-edged triangular graphene molecules (ZTGMs) have been predicted to host ferromagnetically coupled edge states with the net spin scaling with the molecular size, which affords large spin tunability crucial for next-generation molecular spintronics. However, the scalable synthesis of large ZTGMs and the direct observation of their edge states have been long-standing challenges because of the molecules{\textquoteright} high chemical instability. Here, we report the bottom-up synthesis of π-extended [5]triangulene with atomic precision via surface-assisted cyclodehydrogenation of a rationally designed molecular precursor on metallic surfaces. Atomic force microscopy measurements unambiguously resolve its ZTGM-like skeleton consisting of 15 fused benzene rings, while scanning tunneling spectroscopy measurements reveal edge-localized electronic states. Bolstered by density functional theory calculations, our results show that [5]triangulenes synthesized on Au(111) retain the open-shell π-conjugated character with magnetic ground states.}, doi = {10.1126/sciadv.aav7717}, author = {Jie Su and Mykola Telychko and Pan Hu and Gennevieve Macam and Pingo Mutombo and Hejian Zhang and Yang Bao and Fang Cheng and Zhi-Quan Huang and Zhizhan Qiu and Sherman J. R. Tan and Hsin Lin and Pavel Jel{\'\i}nek and Feng-Chuan Chuang and Jishan Wu and Jiong Lu} } @inproceedings {gomcSPP2019, title = {Classification of chest radiographs using depthwise separable convolution}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-21}, address = {Tagbilaran City, Philippines}, abstract = {Pneumonia x-ray images were classified using a neural network with depthwise separable convolutions. Each image was divided into three vertical regions and convolutions were applied to each region independently. The training model has less training parameters than a standard convolutional neural network (CNN) so that the tendency for overfitting and overall computation time is reduced. The trained network features a relatively high precision (ratio of true and predicted positives) and a significantly shorter training time than a conventional CNN. Our preliminary results indicate that the precision of the neural network was not greatly affected by the introduction of depthwise separable convolutions.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-21}, author = {Mary Chris R. Go and Francis N. C. Paraan} } @inproceedings {medranoSPP2019, title = {Computational fluid dynamics analysis of downforce and drag generated by an accessory flat plate wing on the Teardrop 2.0}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-50}, address = {Tagbilaran City, Philippines}, abstract = {We use computational fluid dynamics to calculate the hydrodynamic downforce generated by an accessory flat plate wing when attached to a model of the Teardrop 2.0 submersible. The Teardrop 2.0 is a towed submersible device used to survey shallow coral reefs. In operation, the Teardrop 2.0 can experience unintended changes in depth due to lift and cable tension from drag. In this study, a full scale computer generated reconstruction of the Teardrop 2.0 is fitted with a flat plate wing. This model is then subjected to fluid tunnel simulations using CFD software. At fixed operating speeds, the modified Teardrop 2.0 is found to increase in downforce and drag. Despite this increase in drag, the addition of the accessory wing is found to lower the drag-to-downforce ratio of the Teardrop 2.0 from 8.5 to 2.7, showing that the accessory wing increases downforce more than it increases drag.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-50}, author = {Matthew R. Medrano and Francis N. C. Paraan} } @article {531, title = {Controlling the nucleophilic properties of cobalt salen complexes for carbon dioxide capture}, journal = {RSC Adv.}, volume = {9}, year = {2019}, pages = {23254}, abstract = {

The nucleophilic properties of cobalt salen complexes are examined using density functional theory to investigate its carbon fixing capacity. In particular, carbon dioxide attack on neutral and anionic cobalt salen molecules is considered. Carbon fixation occurs for the anionic cobalt salen complex and is due to the nucleophilic interaction between the cobalt center and carbon dioxide molecule in a Co dz{\texttwosuperior}{\textendash}CO$_{2}$ π* interaction. A minimum energy path search by a nudged elastic band calculation reveals a lower forward activation energy for the anionic complex than the neutral complex, indicating that the formation of the anionic complex is thermodynamically and kinetically favored. In this case, the CO$_{2}$ molecule is chemisorbed as partial charge transfer from the cobalt center to carbon dioxide is observed. Proposed reaction mechanisms explain how the Co{\textendash}C bond energy of the CO$_{2}${\textendash}cobalt salen complex can be tuned by appropriate substitutions of electron donating or withdrawing groups on the phenyl ring.

}, doi = {10.1039/C9RA01990A}, author = {Meliton R. Chiong and Francis N. C. Paraan} } @article {654, title = {Critical lines in the pure and disordered O(N) model}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2019}, year = {2019}, pages = {024001}, abstract = {We consider replicated O(N) symmetry in two dimensions within the exact framework of scale invariant scattering theory and determine the lines of renormalization group fixed points in the limit of zero replicas corresponding to quenched disorder. A global pattern emerges in which the different critical lines are located within the same parameter space. Within the subspace corresponding to the pure case (no disorder) we show how the critical lines for non-intersecting loops (-2 <= N <= 2) are connected to the zero temperature critical line (N > 2) via the BKT line at N = 2. Disorder introduces two more parameters, one of which vanishes in the pure limit and is maximal for the solutions corresponding to Nishimori-like and zero temperature critical lines. Emergent superuniversality (i.e. N -independence) of some critical exponents in the disordered case and disorder driven renormalization group flows are also discussed.}, doi = {10.1088/1742-5468/aaf716}, url = {https://iopscience.iop.org/article/10.1088/1742-5468/aaf716}, author = {Gesualdo Delfino and Noel Lamsen} } @article {655, title = {Critical points of coupled vector-Ising systems. Exact results}, journal = {J. Phys. A. Math. Theor.}, volume = {52}, year = {2019}, pages = {35LT02}, abstract = {We show that scale-invariant scattering theory allows to exactly determine the critical points of two-dimensional systems with coupled O(N) and Ising order parameters. The results are obtained for N continuous and include criticality of the loop gas type. In particular, for N = 1 we exhibit three critical lines intersecting at the Berezinskii-Kosterlitz-Thouless transition point of the Gaussian model and related to the Z$_{4}$ symmetry of the isotropic Ashkin-Teller model. For N = 2 we classify the critical points that can arise in the XY-Ising model and provide exact answers about the critical exponents of the fully frustrated XY model.}, doi = {10.1088/1751-8121/ab3055}, url = {https://iopscience.iop.org/article/10.1088/1751-8121/ab3055}, author = {Gesualdo Delfino and Noel Lamsen} } @inproceedings {esperanzaSPP2019, title = {Critical scaling at the N{\'e}el transition in an extended Hubbard model with Ising-like interaction}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1G-05}, address = {Tagbilaran City, Philippines}, abstract = {We examine the critical behavior of the von Neumann entanglement entropy and the staggered magnetization order parameter in an extended Hubbard chain across the N{\'e}el transition at half-filling. The order parameter and the entanglement entropy was calculated using density matrix renormalization group (DMRG) for periodic chains with length L = 32, 64, and 100. We demonstrate that the entanglement entropy can locate the quantum critical point. Finite size scaling analyses of the N{\'e}el order parameter and entanglement entropy give estimates for the critical exponents associated with these observables.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1G-05}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {acostaSPP2019, title = {Current amplification and rectification in a chain of four spins individually coupled to different heat baths}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-33}, address = {Tagbilaran City, Philippines}, abstract = {In this work, we considered a linear chain consisting of four spins individually coupled to different heat baths. We calculated numerically the heat currents by solving the transition rate equations as previously discussed in Ref. [1]. The temperature of the heat bath of the first spin is held constant. The temperatures of the second and third heat baths are set to be the average of the heat baths at the edges while the temperature of the fourth heat bath at the edge is allowed to vary from zero to twice the temperature of the first heat bath. We demonstrate that for a chain of spins conjugate to this heat bath temperature configuration, current amplification and rectification are exhibited.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-33}, author = {Geronimo Allan Jerome Acosta and Cristine Villagonzalo} } @inproceedings {gomnSPP2019, title = {Determining higher order periods of the Logistic equation using a Chebyshev Transform}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-12}, address = {Tagbilaran City, Philippines}, abstract = {The Logistic Equation is an iterative equation which exhibits complicated dynamics when the control parameter r is varied. When r is in between 3 and 3.57, a period doubling phenomena occurs in which periods of 2N is observed, where N∈(1,$\infty$). The Time Series of the Logistic Equation can be interpreted using Power Spectrum analysis method in which one can determine the periods present with a given r value. A popular method in determining the Power Spectrum is the Fast Fourier Transform (FFT). A difficulty encountered by the FFT however is presenting the Power Spectrum of higher order periods since the lower order periods have larger magnitudes, making the higher periods barely visible in the plot. In this paper, we explore the possibility of determining the Power Spectrum of the Logistic Equation using a Chebyshev Transform. The transform was constructed with the help of a package in Matlab called Chebfun in extracting the Chebyshev coefficients. The coefficients together with the scaled frequency bin was used in comparison to the power spectrum of the FFT. It was seen that the Chebyshev Transform had larger peaks compared to that of the FFT and had better numerical accuracy when it comes to determining the periods of the time series.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-12}, author = {Michael Nicholas Go and Ronald Banzon} } @inproceedings {guinidSPP2019, title = {Diversity in iteroparous Penna Model with delayed mutations}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-23}, address = {Tagbilaran City, Philippines}, abstract = {The Penna bit string model is used as a framework for the genetic diversity investigations of iteroparous population with delayed mutations. We used a Shannon-type measure to quantify genetic diversity. At stable populations, the diversity decreases with increasing mutation delay. Cases with longer mutation delay have higher populations and extended lifespans.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-23}, author = {Jammy Rey C. Guinid and Ronald Banzon} } @inproceedings {mactalSPP2019, title = {Effects of spatial disorder in modelling the anomalous diffusion of tracer particles on a graphene lattice}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-18}, address = {Tagbilaran City, Philippines}, abstract = {Modern microscopic techniques such as high resolution transmission electron microscopy have been developed by experimentalists in order to track the anomalous diffusion of tracer particles. By using the site percolation model, this paper investigated the effects of spatial disorder on a graphene lattice and how parameters such as the percolation threshold contributes to a significant deviation from the linear diffusion equation. In order to obtain the numerical percolation threshold, a cluster-identifying algorithm was developed. This value was found to be 0.7139 which has a theoretical deviation of 2.542\%. After establishing this, simulations of the particle diffusing on the percolating system with p=0.7139 were done and its mean squared displacement (MSD) at each time step t was extracted. After analysis of the log-log plot of the MSD vs. number of steps taken, it was found that the particle exhibited subdiffusive behavior for the different cases tested because it violated Einstein{\textquoteright}s third condition for linear diffusion.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-18}, author = {Gerard Antonio L Mactal and Cristine Villagonzalo} } @article {597, title = {Engineering surface structure of spinel oxides via high-valent vanadium doping for remarkably enhanced electrocatalytic oxygen evolution reaction}, journal = {ACS Appl. Mater. Interfaces}, volume = {11}, year = {2019}, pages = {33012}, abstract = {Spinel oxides (AB$_{2}$O$_{4}$) with unique crystal structures have been widely explored as promising alternative catalysts for efficient oxygen evolution reactions; however, developing novel methods to fabricate robust, cost-effective, and high-performance spinel oxide based electrocatalysts is still a great challenge. Here, utilizing a complementary experimental and theoretical approach, pentavalent vanadium doping in the spinel oxides (i.e., Co$_{3}$O$_{4}$ and NiFe$_{2}$O$_{4}$) has been thoroughly investigated to engineer their surface structures for the enhanced electrocatalytic oxygen evolution reaction. Specifically, when the optimal concentration of vanadium (ca. 7.7 at. \%) is incorporated into Co$_{3}$O$_{4}$, the required overpotential to reach a certain jGEOM and jECSA decreases dramatically for oxygen evolution reactions in alkaline media. Even after 30 h of chronopotentiometry, the required potential for V-doped Co$_{3}$O$_{4}$ just increases by 16.3 mV, being much lower than that of the undoped one. It is observed that the pentavalent vanadium doping introduces lattice distortions and defects on the surface, which in turn exposes more active sites for reactions. DFT calculations further reveal the rate-determining step changing from the step of *-O to *-OOH to the step of *-OH to *-O, while the corresponding energy barriers decrease from 1.73 to 1.57 eV accordingly after high-valent V doping. Moreover, the oxygen intermediate probing method using methanol as a probing reagent also demonstrates a stronger OH* adsorption on the surface after V doping. When vanadium doping is performed in the inverse spinel matrix of NiFe2O4, impressive performance enhancement in the oxygen evolution reaction is as well witnessed. All these results clearly illustrate that the V doping process can not only efficiently improve the electrochemical properties of spinel transition metal oxides but also provide new insights into the design of high-performance water oxidation electrocatalysts.}, doi = {10.1021/acsami.9b10868}, author = {Renjie Wei and Xiuming Bu and Wei Gao and Rovi Angelo B. Villaos and Gennevieve Macam and Zhi-Quan Huang and Changyong Lan and Feng-Chuan Chuang and Yongquan Qu and Johnny C. Ho} } @inproceedings {gomezSPP2019, title = {Evaporation and compaction of colliding dust clusters at different impact parameters}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-21}, address = {Tagbilaran City, Philippines}, abstract = {The dynamics of colliding dust clusters is important in the study of dust cloud evolution. In this work, a molecular dynamics simulation of the collision of two spherical clusters of SiO$_{2}$ particles was done to find out how the evaporation fraction depends on impact parameter. By measuring the average number of neighbors each unevaporated grain has, we found a critical impact parameter that results in maximum cluster compaction.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-21}, author = {Jacob Gomez and Francis N. C. Paraan} } @inproceedings {riveraSPP2019, title = {Floating point representation error propagation analysis in quantum computing from a fixed point example}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-25}, address = {Tagbilaran City, Philippines}, abstract = {This study is motivated by the search for a minimum precision benchmark required of a binary computer to simulate a quantum computing algorithm. In using the floating point system, there is an inherent representation error due to limited memory of the computer to express numbers that cannot be perfectly represented in binary. The case of a test function iterated about a fixed point was used to demonstrate a procedure for the accounting for error propagation, where the argument is misrepresented to some other value 1/n + δ. For i iterations, the error, δ was found to grow by (n+1)i and decrease at a rate 2-f to mantissa precision. This procedure was applied in the case of quantum computing, to account for the error propagation of a misrepresented qubit and gate ρ = ρ + Δ ρ and G{\textquoteright} = G + ΔG, which was shown for 1 operation.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-25}, author = {Vincent Rivera and Ronald Banzon} } @inproceedings {535, title = {Ground state entanglement in an extended Hubbard model with Ising-like interactions}, booktitle = {AQIS Conference 2019 Abstract Booklet - Poster Day 1}, year = {2019}, month = {19{\textendash}23 Aug 2019}, pages = {164}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {We probe the half-block von Neumann entanglement entropy along with the ground state properties of a 1D extended Hubbard model as its intrasite and intersite interaction parameters are varied. The half-block entanglement entropy was calculated using the density matrix renormalization group (DMRG) for a periodic chain. We demonstrate that the half-block entanglement entropy provides a sketch of the changes in the ground state of the system and that it can be used to locate the quantum critical lines in the model.}, url = {http://aqis-conf.org/2019/program/}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {lopezSPP2019, title = {Image preprocessing with bi-histogram equalization in a supervised classification of radiographs}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-22}, address = {Tagbilaran City, Philippines}, abstract = {Convolutional neural network models are known for their effectiveness in solving computer vision problems. These neural networks are designed to extract features from raw data for accurate classification. The objective of this paper is to study the effects of bi-histogram equalization preprocessing on the performance of a convolutional neural network in identifying pneumonia from a chest x-ray image. The model trained with the preprocessed images demonstrated improved accuracy during training and validation of the neural network.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-22}, author = {Vidal Wyatt M. Lopez and Francis N. C. Paraan} } @inproceedings {adelinoSPP2019, title = {Implementation of a quantum algorithm for solving linear equations}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-10}, address = {Tagbilaran City, Philippines}, abstract = {A quantum algorithm that solves linear systems of equations were proposed by Harrow, Hassidim and Lloyd (HHL) and was implemented in this study using Cirq which is a library in Python used for implementing quantum circuits. Four cases of the quantum circuit implementation were studied: |b〉 is either |0〉 or |+〉, and the number of controlled rotations is either four or six. It has been observed that for larger number of trials per observable, the variance or the fluctuation of the simulated value from the theoretical one becomes smaller. However, the effects of the number of controlled rotations or circuit size to the measured values were not observed.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-10}, author = {Joanne Mae B. Adelino and Ronald Banzon} } @inproceedings {delimaSPP2019, title = {Interlayer and intralayer interactions in a graphene junction beyond nearest neighbors}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-34}, address = {Tagbilaran City, Philippines}, abstract = {The potential applications of the ballistic property of the thermal transport due to phonons in a zigzag graphene junction has prompted scientists to study the material{\textquoteright}s thermal properties. A zigzag graphene junction placed between a heat source and a heat sink has an induced temperature gradient wherein ballistic thermal transport becomes possible. Thermal transport studies for this system are usually characterized at the molecular level by nearest neighbor interactions between the carbon atoms within the junction. This paper aims to derive interlayer and intralayer interactions beyond nearest neighbors using a harmonic interaction potential and highlight their effects. We successfully determined these interactions by taking the Hamiltonian interaction matrix and illustrated a systematic way to add more interactions between graphene interlayers.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-34}, author = {Krishna Lyn Delima and Cristine Villagonzalo} } @inproceedings {naragSPP2019, title = {Investigation on the effect of tensile and compressive strain on the electronic structure of silicene using the density functional theory}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-16}, address = {Tagbilaran City, Philippines}, abstract = {We investigate the effect of tensile and compressive strain on the electronic structure of silicene using the density functional theory as implemented in the Quantum Espresso software. It was found that a tensile strain of about 7\% induces a semimetal-metal transition. Such a transition also occurs for 5\% applied compressive strain. Furthermore, an approximately linear relationship between an increasing strain and conduction (valence) band-Fermi energy difference was obtained for both types of strain. Engineering the band gap can widen the potential applications for mechanical modulation of the electronic properties of silicene.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-16}, author = {Dean Von Johari C. Narag and Cristine Villagonzalo} } @inproceedings {ongkikoSPP2019, title = {Molecular projected band structure of ammonia and ammonium adsorbed on graphene}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PA-17}, address = {Tagbilaran City, Philippines}, abstract = {The electronic structures of ammonia and ammonium molecules adsorbed on pristine graphene are studied in this work. In particular, molecular projected densities of states (MolPDOS) were calculated by density functional theory to characterize these adsorption systems by projecting the eigenstates of the full system onto those of the adsorbate molecule. Ammonium adsorption on graphene exhibited a stronger adsorption than ammonia, indicating the possibility of designing a selective substrate. This difference was also reflected in the MolPDOS-produced band structure by the presence of distinct regions of mixed ammonium and graphene states located around 1 eV above the Fermi level.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PA-17}, author = {Mario Antonio T. Ongkiko and Francis N. C. Paraan} } @inproceedings {villanoSPP2019, title = {Monte Carlo approach to one-dimensional cell proliferation within a tissue-cell population}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-35}, address = {Tagbilaran City, Philippines}, abstract = {The interplay of biological, chemical, and physical factors of cancer cells give rise to its complex behavior. This complexity is one of the main reasons why the cure for cancer remains elusive. Finding a way to predict and understand this stochastic behavior would enable us to develop new and effective treatments that would hopefully lead to a cure for cancer. With this in mind, we constructed an algorithm for a stochastic one-dimensional cell proliferation through agent-based modeling and Monte Carlo methods. The proliferation of cells in a one-dimensional axis is demonstrated for different growth rates and cell-cell attraction strengths.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-35}, author = {Celso T. Villano Jr and Cristine Villagonzalo} } @inproceedings {castroSPP2019, title = {Multi-class semantic segmentation and volume calculation of cardiac CT scans using convolutional neural networks}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-1C-07}, address = {Tagbilaran City, Philippines}, abstract = {Computed tomography (CT) scans from the MICCAI 2017 Multi-Modality Whole Heart Segmentation Challenge dataset were segmented into seven anatomical substructures (left and right ventricles, left and right atria, myocardium, aorta, and pulmonary artery) using the SpatialConfiguration-Net (SCN). The SCN utilizes a U-Net convolutional network architecture that is designed for biomedical image segmentation. The performance of the neural network was evaluated by cross validation on the training data by the Dice Similarity Coefficient over all heart substructures. Improved segmentation of most of the substructures was observed over other proposed convolutional neural network pipelines. While the estimated volumes of the segmented substructures are consistent with the manual annotations, the SCN performed sub-optimally in detecting gaps between heart substructures due to the loss of resolution caused by multilayer down-sampling and up-sampling of the images.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-1C-07}, author = {Marc Jerrone Castro and Francis N. C. Paraan} } @inproceedings {deleonSPP2019, title = {Parallel acceleration of density matrix renormalization group calculations with TensorFlow}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-14}, address = {Tagbilaran City, Philippines}, abstract = {We parallelize singular value decomposition in a matrix product state formulation of the density matrix renormalization group using the TensorFlow library to find use cases in which consumer-grade GPU hardware can reduce run times. Specifically, we tested the performance of the implementation on a 20-site spin chain for a variable number of kept states. We were able to acquire a speedup of up to 6.4\% when using TensorFlow GPU libraries and a speedup of up to 5.4\% with TensorFlow multicore CPU libraries. This speedup is observed when the number of kept states exceeds a threshold value so that the dimensions of the matrices in the calculation are large enough that the gains in parallelization exceed computational overhead costs.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-14}, author = {Kryzz Joshua G. de Leon and Francis N. C. Paraan} } @article {656, title = {On the phase diagram of the random bond q-state Potts model}, journal = {Eur. Phys. J. B}, volume = {92}, year = {2019}, pages = {278}, abstract = {We consider the two-dimensional random bond q-state Potts model within the recently introduced exact framework of scale invariant scattering, exhibit the line of stable fixed points induced by disorder for arbitrarily large values of q, and examine the renormalization group pattern for q > 4, when the transition of the pure model is first order.}, doi = {10.1140/epjb/e2019-100451-6}, url = {https://link.springer.com/article/10.1140/epjb/e2019-100451-6}, author = {Gesualdo Delfino and Noel Lamsen} } @article {598, title = {Quantum phase transition of correlated iron-based superconductivity in LiFe$_{1}$$_{-}$ₓCoₓAs}, journal = {Phys. Rev. Lett.}, volume = {123}, year = {2019}, pages = {217004}, abstract = {The interplay between unconventional Cooper pairing and quantum states associated with atomic scale defects is a frontier of research with many open questions. So far, only a few of the high-temperature superconductors allow this intricate physics to be studied in a widely tunable way. We use scanning tunneling microscopy to image the electronic impact of Co atoms on the ground state of the LiFe$_{1}$$_{-}$ₓCoₓAs system. We observe that impurities progressively suppress the global superconducting gap and introduce low energy states near the gap edge, with the superconductivity remaining in the strong-coupling limit. Unexpectedly, the fully opened gap evolves into a nodal state before the Cooper pair coherence is fully destroyed. Our systematic theoretical analysis shows that these new observations can be quantitatively understood by the nonmagnetic Born-limit scattering effect in an s{\textpm}-wave superconductor, unveiling the driving force of the superconductor to metal quantum phase transition.}, doi = {10.1103/PhysRevLett.123.217004}, author = {Jia-Xin Yin and Songtian S. Zhang and Guangyang Dai and Yuanyuan Zhao and Andreas Kreisel and Gennevieve Macam and Xianxin Wu and Hu Miao and Zhi-Quan Huang and Johannes H. J. Martiny and Brian M. Andersen and Nana Shumiya and Daniel Multer and Maksim Litskevich and Zijia Cheng and Xian Yang and Tyler A. Cochran and Guoqing Chang and Ilya Belopolski and Lingyi Xing and Xiancheng Wang and Yi Gao and Feng-Chuan Chuang and Hsin Lin and Ziqiang Wang and Changqing Jin and Yunkyu Bang and M. Zahid Hasan} } @inproceedings {536, title = {Quantum phase transitions and Schmidt gap closing in a Kitaev chain with long-ranged interactions}, booktitle = {AQIS Conference 2019 Abstract Booklet - Poster Day 1}, year = {2019}, month = {19{\textendash}23 Aug 2019}, pages = {174-175}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {The quantum phase diagram of a generalized Kitaev chain that exhibits long-ranged hopping and pairing is mapped out by looking for sharp changes in the Schmidt gap of a ground state bipartition.Finite-size scaling analysis reveals that the Schmidt gap exhibits universal scaling behavior about the quantum critical lines. The critical exponents found shows that the model displays different properties at the long- and short-range limits of the interaction.}, url = {http://aqis-conf.org/2019/program/}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @inproceedings {coSPP2019, title = {Simulation of continuous-time random walks with anharmonicity}, booktitle = {Proceedings of the 37th Samahang Pisika ng Pilipinas Physics Conference}, year = {2019}, month = {29 May 2019}, pages = {SPP-2019-PB-48}, address = {Tagbilaran City, Philippines}, abstract = {Anomalous diffusion processes are best described and analyzed by a continuous-time random walk (CTRW) formalism. The latter is a generalization of a transport model using random walk processes that are not limited to Markovian systems. Using a robust numerical generation of continuous trajectories based on Langevin equations, sample paths from a CTRW system encountering a nonlinear net force were generated and analyzed. The resultant force comprised of a linear repelling term and an anharmonic term, that is, f(x) = -k$_{1}$ x + k$_{2}$ x{\textthreesuperior}. The effect of anharmonicity through varying the k$_{2}$ values on the trajectories was manifested on the waiting time. This is the time at which the particle is relatively stationary. At a fixed stability index α, the results show that generally, waiting times would increase as k$_{2}$ values increased and that there is an optimum value of k$_{2}$ where the waiting time is longest. These results are compared to the case when only the linear force is present.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2019-PB-48}, author = {Co, Richmond and Cristine Villagonzalo} } @article {498, title = {Strong chemisorption of CO$_{2}$ on B$_{1}$$_{0}${\textendash}B$_{1}$$_{3}$ planar-type clusters}, journal = {J. Phys. Condens. Matter}, volume = {31}, year = {2019}, pages = {145504}, abstract = {

An ab initio density functional study was performed investigating the adsorption of CO$_{2}$ on neutral boron Bₙ (n = 10{\textendash}13) clusters that are characterized by planar and quasiplanar ground-state atomic structures. For all four clusters, we found large chemisorption binding energies, reaching 1.6 eV between CO$_{2}$ and B$_{1}$$_{2}$, with the adsorbed molecule oriented in the plane of the cluster and adsorbed along the cluster edge. A configuration with chemisorbed dissociated CO$_{2}$ molecule also exists for B$_{1}$$_{1}$ and B$_{1}$$_{3}$ clusters. The strong adsorption is due to the bending of the CO$_{2}$ molecule, which provides energetically accessible fully in-plane frontier molecular orbitals matching the edge states of the clusters. At the same time, the intrinsic dipole moment of a bent CO$_{2}$ molecule facilitates the transfer of excess electronic charge from the cluster edges to the molecule.

}, doi = {10.1088/1361-648x/aafebd}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @conference {479, title = {Accuracy of a tensor network-based image classifier saturates with bond dimension}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {P126}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {In the field of physics, tensor networks have been successfully applied to solve for problems requiring high-dimensionality. As data required in data science are also high-dimensional, tensor methods have also gained appreciation as a tool in machine learning. In this study, we have utilized an existing tensor network-based machine learning program to investigate on the role of bond dimension in the learning rate and the learning accuracy in an image classification problem. In our simulation, the increase in bond dimension leads to improved accuracy but easily reached a saturation point where the gains are overshadowed by the computational cost.}, author = {Mykhal Gideoni L. Mangada and Francis N. C. Paraan} } @inproceedings {canoy, title = {Average work done in a ground state quantum quench of the Kitaev chain model with variable-range interactions}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-18}, address = {Puerto Princesa City, Philippines}, abstract = {We study the average work done associated with a ground state quantum quench of the Kitaev chain model with variable-range interactions. We do this by initially preparing an isolated quantum system in the ground state of the initial Hamiltonian at zero temperature. We, then, abruptly change the relative chemical potential parameter. The average work done on the system, which is defined as the difference between the measured energies before and after the quench, is derived and shown to have inflection points at the critical values of the relative chemical potential of the initial Hamiltonian.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-18}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {476, title = {Band structure contribution of adsorbed H$_{2}$ on graphene calculated from molecular orbital projections}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PA-19}, address = {Puerto Princesa City, Philippines}, abstract = {

Density functional theory allows for the first-principles calculation of projected wavefunctions onto orthogonalized atomic wavefunctions. Such calculations can be applied to study the bonding of a molecule onto an adsorbing surface. In particular, these projections allow one to identify the contributions of the adsorbed molecule to the band structure of the whole system. In this paper, we consider a system composed of an H2 molecule adsorbed onto the hollow (H) site in a graphene 3x3 supercell. The adsorbed H2 molecule gives rise to two bands roughly 6 eV on either side of the Fermi energy. These bands may be attributed to the hybridization of the H2 bonding and anti-bonding molecular\ σ\ orbitals and the graphene bands.

}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PA-19}, author = {Mario Antonio T. Ongkiko and Francis N. C. Paraan} } @inproceedings {464, title = {Benchmarking a tensor network-based machine learning algorithm for supervised image classification}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-23}, address = {Puerto Princesa City, Philippines}, abstract = {Real-world data is often scarce and the careful setting of hyperparameters to efficiently train machine learning algorithms is necessary. In this study the role of bond dimension on the performance of an existing tensor network-based machine learning program was benchmarked on the MNIST and fashion-MNIST data sets. In particular, the effects of bond dimension on the accuracy and execution times of the algorithm were investigated. Results show that a bond dimension of less than 100 is sufficient to reach an acceptable classification accuracy, and increasing the bond dimension further extends the execution time and consumes prohibitive amounts of memory without providing a reasonable improvement in accuracy.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-23}, author = {Mykhal Gideoni L. Mangada and Francis N. C. Paraan} } @conference {478, title = {Calculation of the stiffness coefficients and elastic moduli of copper-silver alloy using molecular dynamics simulations}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {F3-5}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {The elastic moduli for different atomic compositions of copper-silver binary alloy were numerically calculated and analyzed using elastic stiffness coefficients acquired from performing molecular dynamics simulations that use embedded atom model potentials. Constant strain rate along different crystallographic directions was employed to obtain the elastic stiffness coefficients while considering the anisotropic behavior of the material. Dependence of the elastic moduli on the atomic composition of copper-silver in selected ranges from 20-80\% and the effect of temperatures from 300-600 K on these properties were also investigated. It is found out that the elastic moduli increase with increasing copper concentration while decreases in value as temperature is increased.}, author = {Jan Fronimarc D. Viloria and Francis N. C. Paraan} } @conference {477, title = {Characterization of a ground state quantum quench of the Kitaev chain model with variable-range interactions using work statistics}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {F3-2}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {We study the work statistics associated with a ground state quantum quench of the Kitaev chain model with variable-range interactions. We do this by initially preparing a system in the ground state of the Hamiltonian at zero temperature. The relative chemical potential parameter, which governs the unbalance between the chemical potential and hopping terms, is then abruptly changed. The variables of the work statistics, i.e., the average work done and work fluctuation, are derived. The average work done and work fluctuations are shown to have inflection points and kinks, respectively, which signal the vanishing of the excitation gap at the critical prequench relative chemical potential.}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {458, title = {Comparison of Python GPU implementations of eigensolvers}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-51}, address = {Puerto Princesa City, Philippines}, abstract = {Python implementations of GPU-based eigensolvers were tested and evaluated. The performance of PyCUDA and scikit-cuda library functions for Python were used and compared to the corresponding ones from the NumPy library. Despite GPU-based cuBLAS routines being faster than their usual NumPy equivalents on the consumer-level hardware used, cuSOLVER function implementations have longer execution times than the NumPy functions. Two Python variants of the tridiagonalization step of the Lanczos algorithm were tested with cuBLAS functions and we showed that a hybrid CPU-GPU approach resulted in an algorithm that was both fast and stable. However, the presented algorithms are still slower than the highly optimized NumPy eigensolver and further optimizations are needed to obtain GPU acceleration in our Python-based eigensolver.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-51}, author = {John Ian Kenneth E. Felismino and Francis N. C. Paraan} } @inproceedings {467, title = {Computational fluid dynamics analysis of lift on the Teardrop 2.0 for different angles of attack}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-2C-04}, address = {Puerto Princesa City, Philippines}, abstract = {The Teardrop 2.0 is a towed, wing shaped device used for the underwater surveying of shallow coral reefs. We use computational fluid dynamics (CFD) to examine the lift forces acting on a model of the Teardrop 2.0 and determine its lift coefficient for different angles of attack. In this study, a full scale computer generated reconstruction of the Teardrop 2.0 is subjected to fluid tunnel simulations using CFD software. It is found that lift is greatest at an attack angle of around 25{\textdegree}. At greater angles of attack, large regions of recirculation form behind the wing. This effect reduces flow past the trailing edge of the wing, causing lift to decrease. The resulting lift coefficient curve is found to be consistent with experimentally determined lift coefficient curves for flat plate wings.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-2C-04}, author = {Matthew R. Medrano and Maricor N. Soriano and Francis N. C. Paraan} } @inproceedings {488, title = {Density functional theory-based determination of the mechanism of electrochemical reduction of CO$_{2}$ to CO by Co(salen) complex}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PA-27}, address = {Puerto Princesa City, Philippines}, abstract = {

We examine a possible mechanism for the electrochemical reduction of carbon dioxide to carbon monoxide with cobalt salen complex, Co(salen), as the catalyst. Density functional theory was used to calculate the ground state energies and reaction energies of possible reaction intermediates. The results indicate that the reduction from [Co(salen)-CO2]- to Co(salen)-CO proceeds via a Co(salen)-COOH intermediate through a proton transfer and a subsequent concerted proton-electron transfer that releases one molecule of water. The catalyst is then regenerated after carbon monoxide dissociates from the complex.

}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PA-27}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @conference {480, title = {Diversity of semelparous populations in a penna model with continuous and periodic mutations}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {P127}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {The Penna-bit string approach is used as a framework for the genetic diversity investigations of continuous and periodic mutation implementations. We quantify genetic diversity with time in Penna model populations using Shannon diversity index as a measure. The absence of deaths due to mutation accumulation removes selection and results to all populations reaching the same genome. We find that periodic mutation in this case allows the population to reach homogeneity at a much larger time than continuous mutations. On the other hand, the presence of selection results to conservation of diversity. We also know that populations under periodic mutation with selection case tend to be more genetically diverse before reaching steady-state diversity than continuous mutation implementation.}, author = {Jammy Rey C. Guinid and Ronald S. Banzon} } @conference {493, title = {Effect of error tolerance probability to the fidelity of a 4-qubit quantum search simulation}, year = {2018}, month = {5{\textendash}9 Nov 2018}, pages = {P.16}, publisher = {2018 ICTP Asian Network School and Workshop on Complex Condensed Matter Systems}, address = {Suranaree University of Technology, Thailand}, abstract = {We simulate the optimized fixed-point quantum search (OFPQS) algorithm with first- and second-nearest neighbor interactions in a 4-qubit Ising spin system using a nonrefocusing technique. In order to perform a single qubit gate, we utilize the coupling interactions to control the neighboring spins. The phase-marking scheme of the OFPQS is implemented using a single rotation about the transverse axis instead of the usual rotation about the field axis. Furthermore, the state of the ancilla is initialized in a superposition of the basis states to avoid the generation of unwanted states. This procedure gives us a probability of finding the target state within the prescribed bound of the OFPQS. Based on this scheme, we investigate the effect of error tolerance probability of the OFPQS to the fidelity of the nonrefocusing implementation.}, url = {https://indico.cern.ch/event/745791/contributions/3202508/}, author = {Neris Sombillo and Ronald Banzon and Cristine Villagonzalo} } @inproceedings {459, title = {Effect of varying the atomic bond stiffness in the heat baths to the thermal conductance of a graphene junction}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-3B-04}, address = {Puerto Princesa City, Philippines}, abstract = {We simulate ballistic thermal transport due to phonons in a graphene junction by letting it interact with heat baths located at its edges and thereby exposing it to a temperature gradient. The bond stretching force constant for the left (L, heat source), central (C, graphene junction) and right (R, heat sink) regions should ideally be the same since they are all made out of graphene with interactions described by the same interatomic potential. But in an experiment, the graphene sheets acting as heat baths are mounted on silicon oxide while the graphene junction in the central region is suspended with a trench underneath it to reduce its coupling to the silicon substrate. In such a case, the force constants may vary from one region to the next. In this paper, we investigate the effect of varying the atomic bond stiffness in the heat baths to the calculated thermal conductance of a graphene junction using the nonequilibrium Green{\textquoteright}s function method. We find that varying the force constants do not have a significant effect as the junction becomes larger and approaches the bulk behavior. At small junctions, the finite-size effect becomes relevant.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-3B-04}, author = {Nica Jane B. Ferrer and Cristine Villagonzalo} } @inproceedings {466, title = {An effective field analysis of magnetic orbit-to-orbit interactions in a two-dimensional electron gas}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-14}, address = {Puerto Princesa City, Philippines}, abstract = {An effective field Schr{\"o}dinger equation accounting for the effect of the magnetic orbit-to-orbit interaction between electrons in a two-dimensional electron gas (2DEG) is considered. This is formulated out from the effective single-particle equation using the Hartree approximation. As a specific example, a 2DEG in a Hall bar with rectangular geometry is considered, where such equation is reduced to a one-dimensional Schr{\"o}dinger equation. The effect of constant and inverse position-dependent magnetic orbit-to-orbit interaction potentials to the energy levels of the 2DEG is calculated perturbatively.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-14}, author = {Daniel F. Marquez and Cristine Villagonzalo} } @inproceedings {450, title = {Entanglement spectrum and entropy scaling in a Kitaev chain with variable-range interaction}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-35}, address = {Puerto Princesa City, Philippines}, abstract = {The entanglement spectrum was calculated for a contiguous block of spins in a Kitaev chain with a power law decay of interactions. Changes in the degeneracies of the four largest eigenvalues of the spectrum identify the quantum critical line separating the paramagnetic and anti-ferromagnetic phases of the model. Effective central charges along the critical lines are calculated by analyzing the finite-size scaling of the entanglement entropy with block length. For power law exponents that correspond to short-ranged interactions the effective central charge is that of free-fermionic models. For longer ranged interactions the obtained central charge deviates from this value.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-35}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @inproceedings {462, title = {Evaluating the performance of a thresholding filter on handwritten images classification task}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-47}, address = {Puerto Princesa City, Philippines}, abstract = {In this paper we evaluate the effect of a thresholding filter on the accuracy and training times of a deep neural network. The filter increases the brightness of each pixel in the input image and then applies a threshold condition that zeroes out values exceeding a preset value. Although the filter is lossy, we demonstrate improved learning performance under some use cases.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-47}, author = {Vidal Wyatt M. Lopez and Francis N. C. Paraan} } @article {653, title = {Exact results for the O(N) model with quenched disorder}, journal = {J. High Energy Phys.}, volume = {2018}, year = {2018}, pages = {77}, abstract = {We use scale invariant scattering theory to exactly determine the lines of renormalization group fixed points for O(N)-symmetric models with quenched disorder in two dimensions. Random fixed points are characterized by two disorder parameters: a modulus that vanishes when approaching the pure case, and a phase angle. The critical lines fall into three classes depending on the values of the disorder modulus. Besides the class corresponding to the pure case, a second class has maximal value of the disorder modulus and includes Nishimori-like multicritical points as well as zero temperature fixed points. The third class contains critical lines that interpolate, as N varies, between the first two classes. For positive N, it contains a single line of infrared fixed points spanning the values of N from √2 - 1 to 1. The symmetry sector of the energy density operator is superuniversal (i.e. N-independent) along this line. For N = 2 a line of fixed points exists only in the pure case, but accounts also for the Berezinskii-Kosterlitz-Thouless phase observed in presence of disorder.}, doi = {10.1007/JHEP04(2018)077}, url = {https://link.springer.com/article/10.1007/JHEP04(2018)077}, author = {Gesualdo Delfino and Noel Lamsen} } @conference {481, title = {Genetic diversity in asexually reproducing populations of the semelparous Penna model}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {P129}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {We quantify the diversity of populations simulated using the Penna model with an entropy of genetic diversity measure by Pan et al. When selection is removed by increasing the resistance to disease, populations result to a zero-steady state diversity. While for cases with selection, greater genetic diversity was achieved by delaying reproduction. It was also found that populations with genetic diversity tend to have increased average lifespan and resilience to epidemics.}, author = {Amancio II Manceras and Ronald S. Banzon} } @inproceedings {455, title = {GPU implementation of singular value decomposition for high rank tensors}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-50}, address = {Puerto Princesa City, Philippines}, abstract = {Programming using the Python API (application programming interface) offers some advantages over using compiled languages. Here we implement a high rank tensor decomposition routine using the TensorFlow library which has native support for utilizing multi-core CPU, GPU, and TPU hardware. Specifically, a singular value decomposition algorithm was performed on a rank-5 tensor. The performance of this Python implementation was compared with a known C++ based library written specifically for tensor manipulations but without native GPU support. We report some use cases where the implementation on a consumer grade GPU was empirically faster than the C++ based library when the rank-5 tensor has more than 2x10E6 elements. With the acceptable performance of the implementation, it may be beneficial to have have a native implementation of tensor network operations on TensorFlow.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-50}, author = {Kryzz Joshua G. de Leon and Francis N. C. Paraan} } @inproceedings {451, title = {Ground state correlation functions of the XY spin chain in a random transverse field}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-44}, address = {Puerto Princesa City, Philippines}, abstract = {The single-body and anomalous (pair) correlation functions of Jordan-Wigner fermions in the ground state of a disordered XY chain are calculated. Disorder is introduced into this system as a site-dependent transverse field taken from a uniform distribution of fixed width and within the ferromagnetic phase. Results show that increasing the disorder strength by increasing the distribution width leads to a more rapid decay of correlations within the bulk. The average local transverse magnetization of the spin chain decreases with increasing disorder strength, having greater fluctuations in the middle bulk of the chain.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-44}, author = {Binladin A Balt and Francis N. C. Paraan} } @inproceedings {457, title = {Ground state entanglement entropy between harmonically confined dipoles}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-53}, address = {Puerto Princesa City, Philippines}, abstract = {We calculate the R{\'e}nyi entanglement entropy between two harmonically confined dipoles when the degrees of freedom associated with one dipole is traced out in the ground state. When the dimer is in a bound state, the ground state wavefunction is a product of two-mode squeezed states and an exact expression for the R{\'e}nyi entanglement entropy is obtained. The entanglement entropy decays as a power of the separation distance between the dipoles and is a maximum at a critical length determined by the effective Bohr radius of the charge and the confinement length of the trapping potential.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-53}, author = {Mignon Frances A. Dumanjog and Francis N. C. Paraan} } @inproceedings {456, title = {Ground state entanglement entropy in a coupled spin-1/2 dimer with Dzyaloshinsky-Moriya interaction}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-52}, address = {Puerto Princesa City, Philippines}, abstract = {We study the ground state entanglement entropy in a spin-1/2 dimer with Dzyaloshinsky-Moriya (DM) and Heisenberg interactions in a Zeeman field. For a fixed magnitude of the DM vector, the ground state entanglement entropy increases from the ferromagnetic to the anti-ferromagnetic limits of the Heisenberg interaction. In the case of anti-ferromagnetic interactions with strong Zeeman splitting there exists a non-zero value of the DM magnitude that minimizes ground state entanglement. A region of the ground state phase diagram is also described where a critical DM magnitude separates separable and maximally entangled ground states.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-52}, author = {Rafael S. dela Rosa and Francis N. C. Paraan} } @article {613, title = {Growth of a predicted two-dimensional topological insulator based on InBi-Si(111)-√7{\texttimes}√7}, journal = {Phys. Rev. B}, volume = {98}, year = {2018}, pages = {121404}, abstract = {Using combined scanning tunneling microscopy (STM) measurements and first-principles electronic structure calculations, we extensively studied the atomic and electronic properties of a √7 -InBi overlayer on Si(111). We propose and demonstrate an effective experimental process to successfully form a large well-ordered √7 surface by depositing Bi atoms on the In-Si(111)4{\texttimes}1 substrate. The STM images exhibit a honeycomb pattern. After performing an exhaustive computational search, we identified the atomic structures of the surface at In and Bi coverages of 6/7 and 3/7 monolayers, respectively. We discovered a trimer model with a lower energy than the previously proposed model. The simulated STM images of trimer models confirm the presence of the honeycomb pattern in accord with our experimental STM images. Most importantly, we found that the surface is robust, preserving the topologically nontrivial phase. Our edge state calculations verify that the InBi overlayer on Si(111) is indeed a two-dimensional (2D) topological insulator (TI). Moreover, hybrid functional calculations result in band gaps up to 70 meV, which is high enough for room-temperature experiments. Our findings lay the foundation for the materials realization of 2D TIs by growing an InBi overlayer on a Si(111) substrate.}, doi = {10.1103/PhysRevB.98.121404}, author = {Chia-Hsiu Hsu and Zhi-Quan Huang and Cho-Ying Lin and Gennevieve M. Macam and Yu-Zhang Huang and Deng-Sung Lin and Tai Chang Chiang and Hsin Lin and Feng-Chuan Chuang and Li Huang} } @inproceedings {468, title = {Harmonic disturbance on the topological phases of a Chern insulator}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-24}, address = {Puerto Princesa City, Philippines}, abstract = {We demonstrate the effect of a harmonic oscillator perturbing potential on the topological phases of a Chern insulator formed from a square lattice with two quantum states per site. For a region with a non-trivial topological phase characterized by a non-zero Chern number, the perturbation introduced an energy gap closing and divided the non-trivial region into three, which possessed a topologically trivial region and two non-trivial regions. The perturbation induced singularities on the Berry curvature which led to the division of the original topologically non-trivial region.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-24}, author = {Dean Von Johari C. Narag and Cristine Villagonzalo} } @inproceedings {469, title = {Impact of the absorption and reflection of signals on the radiation-induced bystander effect}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-22}, address = {Puerto Princesa City, Philippines}, abstract = {The radiation-induced bystander effect (RIBE) implies radiation risks to cells or tissues not directly exposed to radiation. Effects were found to be strong in the low-dose range which humans are exposed to in the environment such as in medical activities and unpredicted accidents. One possible mechanism of RIBE is through signal transmission between irradiated cells and non-irradiated cells. This work modeled signal transmission through a 2D random walk (RW) of signals in a cell-culture medium containing 103 non-irradiated cells. The effect of boundary conditions (reflection vs. absorption) were observed. Results for the reflection case was better suited for experimental data than the absorption case. It showed independence of RIBE with distance from irradiated source.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-22}, author = {Zheina J. Ottong and Cristine Villagonzalo} } @inproceedings {463, title = {Investigating the diffusion of an atom on the graphene lattice}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-04}, address = {Puerto Princesa City, Philippines}, abstract = {Atomic-scale surface diffusion in graphene is of recent interest to determine the viability of single-atom catalysts in functionalized graphene materials. To model such behavior, we study the random walk behavior of an atom in graphene using mean square displacement (MSD). Without the presence of a driving force, the atom performing a random walk on the graphene lattice would expect to follow linear Brownian motion. We confirm this linear behavior by measuring its mean square displacement (MSD). As the atom was given a driving force, the relationship between MSD and time steps begin to follow the properties of anomalous diffusion. The highest values of a was obtained when the atom was restricted to the first six nearest neighbors while the highest diffusion coeffcient Da was obtained when the atom is free to move to all lattice sites. The power-law relationship between MSD and time step can be controlled and serve as a precursor in understanding how the metal atom diffuses on graphene-oxide support.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-04}, author = {Gerard Antonio L Mactal and Cristine Villagonzalo} } @conference {482, title = {Magnetic orbit to orbit interaction in a two-dimensional electron gas}, year = {2018}, month = {18{\textendash}19 June 2018}, pages = {P130}, publisher = {ASTHRDP Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {The orbit to orbit magnetic interaction between electrons in a two-dimensional electron gas (2DEG) is considered. The orbit to orbit interaction is realized by constructing a Lorentz force law of a system of electrons accounting for both Coulomb electrostatic and Biot-Savart magnetostatic interactions, and external fields. From this, a generalized potential energy and Lagrangian is constructed. Using the calculated mechanical momentum, the effective Hamiltonian is expressed from the energy functon where a sufficient order of inverse speed of light is only considered. Using the Hartree approximation, the solution if the many-body Schr{\"o}dinger equation with this Hamiltonian is approximated with an effective single-particle Schr{\"o}dinger equation. From this the effective mean field Schr{\"o}dinger equation is calculated. We look into the effects of the magnetic orbit-to-orbit interactiong through several forms of effective field potential energies.}, author = {Daniel F. Marquez and Cristine Villagonzalo} } @inproceedings {460, title = {Mutation rate and genetic diversity in a Penna Model}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-13}, address = {Puerto Princesa City, Philippines}, abstract = {The Penna bit string model is used as a framework for the genetic diversity investigations of continuous (every time step) and periodic mutation implementations of a semelparous population. We quantify genetic diversity using a Shannon-type measure. The absence of deaths due to mutation accumulation removes selection and results to the entire population reaching the same genome. We find that periodic mutation in this case allows the population to reach homogeneity at a much later time compared to the case of continuous mutations. Our results indicate that periodic mutation with selection has a higher genetic diversity compared to that of continuous mutation.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-13}, author = {Jammy Rey C. Guinid and Ronald Banzon} } @inproceedings {472, title = {The next-next-nearest neighbor interaction of two Fibonacci anyons}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-3B-03}, address = {Puerto Princesa City, Philippines}, abstract = {The interaction between the next-next-nearest neighboring Fibonacci anyons was observed. The union requires the greatest proximity between the particles, hence the need for two braiding processes. The outcome of the fusion is projected onto the trivial channel, to signify a preference to the ferromagnetic state (i.e., having a negative coupling strength constant). The next-next-nearest neighbor interaction is shown to be more favorable than the next-nearest neighbor interaction.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-3B-03}, author = {Celso T. Villano Jr and Cristine Villagonzalo} } @conference {494, title = {Numerical method for solving the semiclassical Boltzmann equation on multilayer heterogeneous structures}, year = {2018}, month = {5{\textendash}9 Nov 2018}, pages = {P.27}, publisher = {2018 ICTP Asian Network School and Workshop on Complex Condensed Matter Systems}, address = {Suranaree University of Technology, Thailand}, abstract = {We adapt the method developed by D.R. Penn and M. D. Stiles to implement a numerical solution to the semi-classical Boltzmann Equation on multilayer heterogeneous systems. This involves discretization of the linearized spin-independent Boltzmann Equation where the solution for each layer, considered as a bulk material, is obtained. The solutions for the different layers are then joined using boundary conditions at the interfaces to get the result for the whole multilayer structure. This method does not exploit the relaxation time approximation thus produces wider applicability especially to materials that cannot be considered to have a free-electron structure. The resulting distribution function is then used to calculate for the current density for a multi-layered material under a constant external electric field.}, author = {April Cortez and Cristine Villagonzalo} } @inproceedings {449, title = {Piezoelectric tensor of AlN calculated by the Berry phase approach implemented in Quantum ESPRESSO}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-12}, address = {Puerto Princesa City, Philippines}, abstract = {

The proper piezoelectric tensor of AlN was determined using the changes of the Berry phases in response to axial and shear strains in the linear regime. Phases arose from the variation of the wavevector of the Bloch states. Calculations were done in the Quantum ESPRESSO software package using Vanderbilt{\textquoteright}s formulation of the proper piezoelectric tensor. The maximum longitudinal piezoelectric modulus |eij|max coefficient of 1.461 C/m2 was found when both the change in the Berry phase and strain were along the c-axis.

}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-12}, author = {Paul Daniel S. Ang and Francis N. C. Paraan} } @article {612, title = {Prediction of quantum anomalous hall effect in MBi and MSb (M: Ti, Zr, and Hf) honeycombs}, journal = {Nanoscale Res. Lett.}, volume = {13}, year = {2018}, pages = {43}, abstract = {The abounding possibilities of discovering novel materials has driven enhanced research effort in the field of materials physics. Only recently, the quantum anomalous hall effect (QAHE) was realized in magnetic topological insulators (TIs) albeit existing at extremely low temperatures. Here, we predict that MPn (M =Ti, Zr, and Hf; Pn =Sb and Bi) honeycombs are capable of possessing QAH insulating phases based on first-principles electronic structure calculations. We found that HfBi, HfSb, TiBi, and TiSb honeycomb systems possess QAHE with the largest band gap of 15 meV under the effect of tensile strain. In low-buckled HfBi honeycomb, we demonstrated the change of Chern number with increasing lattice constant. The band crossings occurred at low symmetry points. We also found that by varying the buckling distance we can induce a phase transition such that the band crossing between two Hf d-orbitals occurs along high-symmetry point K2. Moreover, edge states are demonstrated in buckled HfBi zigzag nanoribbons. This study contributes additional novel materials to the current pool of predicted QAH insulators which have promising applications in spintronics.}, doi = {10.1186/s11671-017-2424-y}, author = {Zhi-Quan Huang and Wei-Chih Chen and Gennevieve M. Macam and Christian P. Crisostomo and Shin-Ming Huang and Rong-Bin Chen and Marvin A. Albao and Der-Jun Jang and Hsin Lin and Feng-Chuan Chuang} } @article {614, title = {Prediction of two-dimensional organic topological insulator in metal-DCB lattices}, journal = {Appl. Phys. Lett.}, volume = {113}, year = {2018}, pages = {233301}, abstract = {Based on first-principles calculations, we systematically investigated a two-dimensional (2D) organometallic framework consisting of metal atoms (elements from groups IIIA, IVA, VA, VIA, IB, and Pt) and dicyanobenzenes (DCBs). Our stability analysis showed that the system prefers the buckled structure in metals with p-orbital valence electrons, whereas in metals with d-orbitals, the planar phase is preferable. Topological invariants (Z$_{2}$) of these systems were calculated, and they are identified as 2D intrinsic organic topological insulators. Au- and Bi-DCB are exemplar materials with the largest bandgaps within IB and VA groups. Moreover, Au-DCB exhibits robustness of its topological phase against strain. Furthermore, the topologically protected edge states in Au-DCB are identified to further verify the Z$_{2}$ invariant. Interestingly, utilizing hole doping in Bi-DCB leads to a nearly flat Chern band and results in the quantum anomalous Hall phase. Our results suggest that these organometallic frameworks are promising for potential applications in quantum spintronics with the merits of low cost and ease of synthesis.}, doi = {10.1063/1.5064610}, author = {Chia-Hsiu Hsu and Zhi-Quan Huang and Gennevieve M. Macam and Feng-Chuan Chuang and Li Huang} } @inproceedings {470, title = {Radioactive diffusion without complete signal annihilation}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-19}, address = {Puerto Princesa City, Philippines}, abstract = {The radiation-induced bystander effect (RIBE) is a non-contact phenomenon in which cells undergo genetic mutations despite the lack of a direct radiation traversal. In traditional models of the effect, the radiation-carrying signals travel through a medium via random walks and are annihilated upon causing successful mutations. In this paper, we analyze the effect of removing immediate signal annihilation upon successful contact. We find that the removal of immediate signal annihilation is significant only when the initial dosage, the mean number of re-emitted signals, or the probability of mutations are high. Future researchers may take the result into consideration when building models of RIBE.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-19}, author = {Eduard Renzo Santos and Cristine Villagonzalo} } @inproceedings {461, title = {Symmetry-protection in the deformed Affleck-Kennedy-Lieb-Tasaki state}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PB-18}, address = {Puerto Princesa City, Philippines}, abstract = {The Haldane phase captured by the Affleck-Kennedy-Lieb-Tasaki (AKLT) state is a symmery-protected topological (SPT) phase protected by a set of symmetries: either inversion symmetry (IS), time-reversal symmetry (TRS) or the dihedral group of p rotations about two orthogonal axes (D2). This symmetry-protection follows from how the state transforms in its matrix product state (MPS) form under a certain symmetry operation. We study the q-deformed AKLT (AKLTq) state which also has a known MPS form that continuously transforms to that of an AKLT state and how this symmetry-protection is altered. We show that the AKLTq state can be adiabatically connected to the AKLT state when IS is protected. However, our approach does not conclusively lead to the similar conclusion for TRS and D2 , hence, we discuss possible explanations.}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PB-18}, author = {Gene M M Itable and Francis N. C. Paraan} } @inproceedings {471, title = {Two-dimension Ising model simulation via Monte Carlo method with regions without spin}, booktitle = {Proceedings of the 36th Samahang Pisika ng Pilipinas Physics Conference}, year = {2018}, month = {6{\textendash}9 June 2018}, pages = {SPP-2018-PC-32}, address = {Puerto Princesa City, Philippines}, abstract = {We investigate Ising spins in a 2D lattice with a nonmagnetic region. Simulations of increasing regions without spin suggest an effective change in dimensionality: from a system with an effective critical temperature (2D) to one without (1D).}, url = {https://paperview.spp-online.org/proceedings/article/view/SPP-2018-PC-32}, author = {Kryss Urbano and Ronald Banzon} } @inproceedings {chiong, title = {Ab initio study on the binding of carbon dioxide to cobalt salen complex}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-3B-05}, address = {Cebu City, Philippines}, abstract = {Metal-organic complexes, such as metal-Schiff bases, can function as catalysts for electrochemical reduction. In this work we present first principles electronic structure calculations for the adduct formation involving carbon dioxide (CO2) and cobalt salen [Co(salen)] complex. Binding energy calculations show that carbon dioxide forms a stable adduct with [Co(salen)]$^{-}$ complex. The bonding between carbon dioxide and the cobalt metal center involves back-bonding mainly between the metal dz2 orbital and the π* orbital of CO2. An accompanying partial charge transfer from Co to CO2 was observed. This study can be used as a preliminary result to further study the structure and stability of other cobalt-carbon complexes.}, url = {http://paperview.spp-online.org/proceedings/article/view/152}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @conference {chiong2017, title = {Ab initio study on the effects of phenyl substitution on the binding of carbon dioxide to salcomine}, year = {2017}, month = {24{\textendash}26 May 2017}, pages = {147}, publisher = {12th Siam Physics Congress}, address = {Rayong, Thailand}, abstract = {Metal-organic complexes, such as metal-porphyrins, can function as homogeneous catalysts for electrochemical reduction. In this work we present ab initio electronic structure calculations for a reaction involving carbon dioxide and salcomine, a coordination complex consisting of a salen ligand and a cobalt (II) atom. Changes to the binding energy due to substitutions on the phenyl ring by different functional groups are also studied. Cases where a shrinking HOMO-LUMO gap decreases the overpotential and increases the catalytic efficiency of the complex are analyzed. This study provides a theoretical basis for possible salen complex candidates as electrocatalyst for the reduction of carbon dioxide.}, url = {https://indico.cern.ch/event/486350/contributions/2493722/}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @conference {manceras2017spc, title = {An advantage of greater diversity}, year = {2017}, month = {24{\textendash}26 May 2017}, pages = {126}, publisher = {12th Siam Physics Congress}, address = {Rayong, Thailand}, abstract = {We find greater genetic diversity in a Penna model when the mutation threshold is less than the reproductive age, for the case of individuals reproducing only once in their lifetime. This greater diversity is obtained at the cost of decreased saturation population. An increased mean lifespan was obtained for the population with greater genetic diversity. We interpret this longer lifespan as a benefit that supports the idea that it is better to have greater genetic diversity.}, url = {https://indico.cern.ch/event/486350/contributions/2493755}, author = {Amancio II Manceras and Ronald Banzon} } @inproceedings {sombillo, title = {Amplitude amplification of the marked states in quantum search simulation}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-17}, address = {Cebu City, Philippines}, abstract = {Yoder et al. [1] proposed a quantum search algorithm that prevents the system to move away from the marked states when the number of target states M is unknown. This method uses a recursive approach that makes the target state act as a fixed-point. We simulate the algorithm in an Ising spin chain with first- and second-nearest neighbor interaction. Our method involves a selective phase-shift rotation per iteration to obtain the target state. We find the probability of success for the fixed-point implementation to fluctuate only about a limited range of values within an indicated tolerance as compared to the large oscillations of the same for Grover{\textquoteright}s non-fixed-point algorithm.}, url = {http://paperview.spp-online.org/proceedings/article/view/142}, author = {Neris Sombillo and Ronald Banzon and Cristine Villagonzalo} } @inproceedings {elegado, title = {Avoiding artificial deaths in a Penna model population}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-32}, address = {Cebu City, Philippines}, abstract = {In the Penna model, deaths by old age are known to artificially truncate age demographics. We propose to avoid these deaths by obtaining a parameter space plot (Penna parameters R and T, here constrained to a birth rate B=8) for which these deaths do not occur. For both TR, the genetic diversity and number of species decreased more slowly in populations with old age deaths than those without. This confirms a difference in the genetic evolution of these populations.}, url = {http://paperview.spp-online.org/proceedings/article/view/245}, author = {Christopher Patrick P. Elegado and Ronald Banzon} } @conference {canoy2017, title = {Block purity in a long-range Kitaev chain}, year = {2017}, month = {24{\textendash}25 May 2017}, pages = {153}, publisher = {2nd International Science Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {The purity of blocks of 10- and 30-spins in a long-range Kitaev model is calculated by exact diagonalization. The obtained block purity is a measure of entanglement and number fluctuations between the block and the chain it is embedded in. A phase diagram is constructed from the purity when it is expressed as a function of the range parameter and relative chemical potential. It is found that the block purity can differentiate between the magnetic phases of the long-range Kitaev model: it is small in the region corresponding to the antiferromagnetic phase and large in the paramagnetic region.}, author = {Raymart Jay E. Canoy and Francis N. C. Paraan} } @inproceedings {esperanza, title = {Correlations in an extended Hubbard model with Ising-like interaction}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-08}, address = {Cebu City, Philippines}, abstract = {Density-density and spin-spin correlations are calculated in an extended Hubbard model with an intersite Ising-like interaction. Local expectation values and correlation functions involving charge density and magnetization are obtained using the density matrix renormalization group (DMRG) for a periodic chain of L = 10 sites at half-filling. Antiferromagnetic phases with spin and charge density modulation are identified and located in a phase diagram.}, url = {http://paperview.spp-online.org/proceedings/article/view/56}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @inproceedings {acosta, title = {Derivation of heat transport equations for a chain of four interacting spins individually coupled to different heat baths}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-02}, address = {Cebu City, Philippines}, abstract = {In this work we considered a linear chain consisting of four (4) spins individually coupled to different heat baths. For this configuration, we used the quantum master equation to derive the heat currents in terms of transition rates. We obtain a set of linear equations that can be solved explicitly to get the transition rates.}, url = {http://paperview.spp-online.org/proceedings/article/view/42}, author = {Geronimo Allan Jerome Acosta and Cristine Villagonzalo} } @conference {434, title = {A DFT-based determination of the mechanism of electrochemical reduction of CO$_{2}$ to CO by a cobalt-Schiff base catalyst}, year = {2017}, month = {8{\textendash}10 Nov 2017}, pages = {P024}, publisher = {9th Electronic Structure and Processes at Molecular-Based Interfaces Workshop}, address = {National University of Singapore, Singapore}, abstract = {

We perform density functional theory (DFT) based calculations to investigate the reduction of carbon dioxide CO2 to carbon monixide CO using a cobalt-Schiff base catalyst, Co(salen). DFT calculated formation energies and reduction potentials showed that CO2 is reduced to CO via a [Co(salen)-COOH] intermediate. The first step of the mechanism involves the reduction of electrically neutral [Co(salen)]\ to [Co(salen)]-\ anion, followed by an electrophilic addition of CO2. Furthermore, the sigma bond formed between cobalt metal center and\ CO2\ involves a back-donation and partial charge transfer from cobalt to carbon. [Co(salen)-COOH] is further reduced to [Co(salen)-CO] and CO is released from the catalyst along with water H2O.

}, author = {Meliton R. Chiong III and Francis N. C. Paraan} } @inproceedings {itable, title = {Effect of opposite-spin coupling on the edge states of two-dimensional topological insulator}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-13}, address = {Cebu City, Philippines}, abstract = {The Bernevig-Hughes-Zhang model for a two-dimensional topological insulator, insulator with conducting edges, is modified. In particular, we introduce a coupling between opposite spins that preserves the model{\textquoteright}s time reversal invariance. We derive the wave function and the existence conditions for the edge states. With these conditions and tight-binding calculations, we show that that the edge states are robust when the coupling is weak and lesser than the material parameter characterizing the spin-orbit coupling.}, url = {http://paperview.spp-online.org/proceedings/article/view/101}, author = {Gene M. M. Itable} } @conference {432, title = {Entanglement between spin and orbital degrees of freedom in a 2D electron gas}, year = {2017}, month = {18{\textendash}22 Sept 2017}, pages = {1}, publisher = {International Workshop on Non-linear Effects and Short-time Dynamics in Novel Superconductors and Correlated Spin-orbit Coupled Systems}, address = {Daejeon, South Korea}, abstract = {The Rashba interaction couples spin and orbital degrees of freedom in a two-dimensional electron gas. A Landau level basis leads to an equivalent spin-boson model that couples adjacent Landau levels. We study the entanglement between the spin and orbital subspaces in the ground state of a gas of electrons described by this Hamiltonian. The spin-orbit entanglement entropy as a function of filling factor is piecewise smooth with discontinuous derivatives due to gapped levels of degenerate orbitals and level crossings.}, url = {http://pcs.ibs.re.kr/PCS_Workshops/PCS_NLST2017.html}, author = {Francis N. C. Paraan and Rona F Barbarona} } @conference {435, title = {Entanglement entropy in a spin-boson model and level crossings in an Ising dimer with Dzyaloshinskii-Moriya interaction}, year = {2017}, month = {20{\textendash}24 Nov 2017}, pages = {P.11}, publisher = {2017 ICTP Asian Network School and Workshop on Complex Condensed Matter Systems}, address = {Institute of Physics, Vietnam Academy of Science and Technology, Hanoi, Vietnam}, abstract = {We calculate the entanglement entropy between a spin and bosonic modes in a spin-boson model using different ground state ansatze. The entanglement entropy saturates exponentially to a constant as the value of the displacement parameters of the boson modes is increased. We also search for level crossings in a system composed of two spins coupled by a Dzyaloshinkskii-Moriya interaction.}, url = {https://www.iop.vast.ac.vn/theor/conferences/asian/2017/program.php}, author = {Rafael S. dela Rosa and Francis N. C. Paraan} } @conference {420, title = {Fixed-point quantum search as implemented in an Ising spin system}, year = {2017}, month = {26{\textendash}29 June 2017}, pages = {50}, publisher = {6th Adiabatic Quantum Computing Conference}, address = {Tokyo, Japan}, abstract = {The fixed-point quantum search provides a solution to the oscillation problem in a quantum search algorithm through the variation of oracle and inversion phases at each iteration. We simulate the fixed-point algorithm in an Ising spin system with first- and second-nearest neighbor interactions. Since the oracle and the inversion operator acts on O(2), then the oracle qubit is required to be in a superposition of states at the start of the simulation. This provides a way to implement the rotation required in the variation of phases at each iteration. Results show that the probability of success calculated from the algorithm and obtained from the simulation gives a similar behavior which effectively damps the oscillation. We also investigate the effect of tolerance on the fidelity as we increase the number of iterations.}, url = {http://www.smapip.is.tohoku.ac.jp/~aqc2017/program.html}, author = {Neris I Sombillo and Ronald S. Banzon and Cristine Villagonzalo} } @inproceedings {ferrer, title = {Implementing the nonequilibrium Green{\textquoteright}s function method in calculating the phonon transmission in a graphene lattice}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-1C-06}, address = {Cebu City, Philippines}, abstract = {The phonon transmission in a graphene lattice was determined using the nonequilibrium Green{\textquoteright}s function (NEGF) method. The transport system consists of a graphene lattice that was connected to semi-infinite thermal leads. These leads induce a temperature gradient across the central lattice. To achieve ballistic transport, the leads were also chosen to be graphene lattices. Through the NEGF method, the effect of the leads are easily projected to the central lattice via the self-energies Σrα. The decimation method was used to obtain the retarded surface Green{\textquoteright}s functions for the semi-infinite thermal leads grα(ω). After which, the phonon transmission function χ(ω) was calculated using the Caroli formula for the central region. The phonon transmission as a function of ω was obtained for the first and second renormalizations of the Green{\textquoteright}s functions in the decimation method.}, url = {http://paperview.spp-online.org/proceedings/article/view/145}, author = {Nica Jane B. Ferrer and Cristine Villagonzalo} } @inproceedings {ang, title = {Linear elastic and piezoelectric response of BaNiO3 to strain}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-36}, address = {Cebu City, Philippines}, abstract = {Preliminary ab initio calculations were done in Quantum ESPRESSO to obtain the piezoelectric coefficients of BaNiO3 by computing the stress and polarization induced by strain. The linear elastic response to strain was investigated under the six deformation modes to obtain full elastic stiffness tensor. A linear polarization response was found using the Berry-phase method. These results would be utilized in future work to calculate the piezoelectric coefficients of BaNiO3 and other perovskites.}, url = {http://paperview.spp-online.org/proceedings/article/view/209}, author = {Paul Daniel S. Ang and Francis N. C. Paraan} } @inproceedings {trinidad, title = {Local periodicity of migrating populations in the Penna model}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-18}, address = {Cebu City, Philippines}, abstract = {Migrating populations are considered under two conditions: migrating threshold based on the population{\textquoteright}s non-migrating steady state population for each value of R, and migrations of newborns to a random nearest neighbor site. We determined that the time series of the migrating populations result to multiple periods on single runs, but single when averaged over 50 runs for all values of R in all sites in the lattice.}, url = {http://paperview.spp-online.org/proceedings/article/view/210}, author = {Jhames Ni{\~n}o T. Trinidad and Ronald Banzon} } @article {377, title = {Measurement-enhanced quantum search}, journal = {AIP Conf. Proc. (8th Jagna International Workshop)}, volume = {1871}, year = {2017}, pages = {020002}, abstract = {The oscillatory nature of the unitary Grover operator makes quantum searching difficult if one has no prior knowledge of the number of target states in the database. In this work, we coupled the database to an external qubit to transfer the target state in a space where the quantum search operation is not applied. This is followed by a measurement of the external and the ancilla qubit which result to a mixed state with a higher probability of finding the target state. The algorithm is simulated in a spin chain having first and second order neighbor interactions. The result shows that the oscillation is suppressed and the probability of success generally increased with iteration number.}, doi = {10.1063/1.4996512}, url = {http://aip.scitation.org/doi/10.1063/1.4996512}, author = {Neris I Sombillo and Ronald Banzon and Cristine Villagonzalo} } @inproceedings {viloria, title = {Molecular dynamics calculation of the elastic constants of quenched FeNi and FeCr alloys}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-2B-03}, address = {Cebu City, Philippines}, abstract = {Molecular dynamics simulations were conducted to obtain the elastic constants of quenched FeNi and FeCr alloys at different atomic compositions. The simulation was conducted using an embedded atom model (EAM) potential and the alloys were subjected to a rapid cooling from 1273 K to 298 K. Deformation process was performed along different crystallographic directions at a constant strain rate. The calculated elastic constants of quenched FeNi and FeCr alloys are in good agreement to experimental data with 1-12\% difference in values. Accuracy of the results were associated with the structural phase and transferability of the EAM potential at higher temperatures.}, url = {http://paperview.spp-online.org/proceedings/article/view/121}, author = {Jan Fronimarc D. Viloria and Francis N. C. Paraan} } @inproceedings {fernandez, title = {Molecular dynamics calculation of the reduced glass transition temperature for a copper-silver metallic glass}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-2B-06}, address = {Cebu City, Philippines}, abstract = {A molecular dynamics simulation with an embedded atom method (EAM) potential was performed to simulate metallic glass formation in a 32000-atom cubic supercell of a Cu64 Ag36 alloy. The obtained cooling curve and pair distribution function possess features that support the formation of a metallic glass. The reduced glass transition temperature Trg was calculated to be 0.53, which passes the Turnbull criterion for good metallic glass formers.}, url = {http://paperview.spp-online.org/proceedings/article/view/123}, author = {Zed Harold E. Fernandez and Francis N. C. Paraan} } @conference {viloria2017, title = {Molecular dynamics study of the elastic properties of copper-silver alloy using embedded atom model potential}, year = {2017}, month = {24{\textendash}26 May 2017}, pages = {164}, publisher = {12th Siam Physics Congress}, address = {Rayong, Thailand}, abstract = {The elastic properties of copper-silver alloy were determined for different atomic compositions by molecular dynamics simulations using an embedded atom model (EAM) potential. The elastic constants (c11, c12, c44) that describe the Young{\textquoteright}s modulus, bulk modulus, and shear modulus, were obtained from the stress-strain curves using strains applied at a constant rate. The temperature dependence of the elastic properties from 300K to 600K is also reported.}, url = {https://indico.cern.ch/event/486350/contributions/2493723/}, author = {Jan Fronimarc D. Viloria and Francis N. C. Paraan} } @inproceedings {medrano, title = {Quantitative analysis of fluid flow around the Towpedo via computational fluid dynamics}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-3B-04}, address = {Cebu City, Philippines}, abstract = {The Towpedo is a torpedo-shaped device used to conduct rapid and wide-range photographic surveys of shallow coral reefs. The objectives of this study were to determine the forces acting on a Towpedo moving in seawater and determine its drag coefficient via computational fluid dynamics. A computer generated model of the Towpedo was subjected to fluid tunnel simulations using computational fluid dynamic software. The results revealed regions of highest pressure at the nose of the Towpedo, while forces acting perpendicular to the direction of motion were relatively small compared to the drag force acting along the direction of flow. Resulting drag force was also found to exhibit a quadratic relationship with velocity, which is consistent with empirical models of drag. From these results, the drag coefficient of the Towpedo was determined.}, url = {http://paperview.spp-online.org/proceedings/article/view/213}, author = {Matthew R. Medrano and Apolinario Miguel I. Tan and Aaron T. Hilomen and Maricor N. Soriano and Francis N. C. Paraan} } @inproceedings {balt, title = {Quasi-particle excitation spectrum of an XY spin chain in a random transverse field}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-27}, address = {Cebu City, Philippines}, abstract = {The quasi-particle excitation spectrum of an XY spin chain in a random transverse field was calculated by an exact singular value decomposition. The spectrum was found to be robust at small disorder strengths and deep within the paramagnetic phase. For larger disorder strengths, and about the ferromagnetic region, the spectrum deviated further from the quasi-excitation spectrum of the ordered chain. These deviations lead to the disorder-averaged ground state energy E0 to increase with disorder strength, even as the average field strength remains constant.}, url = {http://paperview.spp-online.org/proceedings/article/view/170}, author = {Binladin A Balt and Francis N. C. Paraan} } @inproceedings {santos, title = {The radio-biological bystander effect as a non-linear diffusive phenomenon}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-3B-03}, address = {Cebu City, Philippines}, abstract = {The radiation-induced bystander effect (RIBE) is a phenomenon in which cells undergo genetic damage without having been directly irradiated by an external radiation source. In current literature, it is often modeled via Monte Carlo simulations with the standard Brownian motion as the underlying mode of diffusion. In this study, we replace the standard Brownian motion with the fractional Brownian motion (fBm) and compare it with previous experimental data. We note that the ensemble probability of irradiation is slightly higher in the subdiffusive regime as compared to the standard Brownian motion, which tends to underestimate it. Furthermore, the uniformity of irradiation is preserved in the subdiffusive regime. For these reasons, we conclude that the radio-biological bystander effect is more appropriately examined in the subdiffusive regime (H < 1/2).}, url = {http://paperview.spp-online.org/proceedings/article/view/74}, author = {Eduard Renzo Santos and Cristine Villagonzalo} } @inproceedings {generalao, title = {Reducing execution times of Quantum ESPRESSO PWscf calculations by routing matrix multiplication calls to GPUs}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-05}, address = {Cebu City, Philippines}, abstract = {We report significant decreases in execution times of plane-wave self consistent field (PWscf) calculations on the software suite Quantum ESPRESSO (QE) by routing general matrix multiplication calls to graphical processing units. The approach described here does not require source code modifications nor recompilation. Running the standard benchmark test AUSURF112 on a single 2.0 Ghz core with two threads showed that using two commodity GPU cards can halve PWscf execution times.}, url = {http://paperview.spp-online.org/proceedings/article/view/222}, author = {Oliver B. Generalao and Francis N. C. Paraan} } @inproceedings {manceras, title = {Resilience in a semelparous Penna model}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-3B-06}, address = {Cebu City, Philippines}, abstract = {We consider the effect of a harsher environment on Penna populations with different genetic diversities. A change in the environment, in the form of an epidemic, is simulated by a lowering of the mutation threshold. Our results suggest that populations with greater genetic diversity have a greater probability of survival during an epidemic.}, url = {http://paperview.spp-online.org/proceedings/article/view/132}, author = {Amancio II Manceras and Ronald Banzon} } @conference {436, title = {The role of orbit to orbit magnetic interaction in a two-dimensional electron gas in the quantum Hall regime}, year = {2017}, month = {20{\textendash}24 Nov 2017}, pages = {P.5}, publisher = {2017 ICTP Asian Network School and Workshop on Complex Condensed Matter Systems}, address = {Institute of Physics, Vietnam Academy of Science and Technology, Hanoi, Vietnam}, abstract = {The orbit to orbit magnetic interaction between electrons in a quantum Hall system is considered. The standard method in the presence of scalar Coulomb interaction potential and external electromagnetic fields is to express the mechanical momentum as p + eA in the effective Hamiltonian. The orbit to orbit interaction is realized by constructing an effective system Hamiltonian possessing a magnetic interaction vector potential in the mechanical momentum. The resulting many-body Schr{\"o}dinger equation with this Hamiltonian is solved to calculate the electron density and potential energy profiles. The aim of this work is to see the effect of the orbit to orbit interaction in calculating the compressibility of the electron gas in the quantum Hall regime.}, url = {https://www.iop.vast.ac.vn/theor/conferences/asian/2017/program.php}, author = {Daniel F Marquez and Cristine Villagonzalo} } @inproceedings {ayang-ang, title = {Schmidt gaps in a long-range Kitaev chain}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-1C-04}, address = {Cebu City, Philippines}, abstract = {The Schmidt gap for a block of spins in an infinite long-range Kitaev chain is calculated as a function of interaction range and the relative strengths of the chemical potential and hopping terms. We find that for long-ranged interactions where area law violations to the entanglement entropy occur, the Schmidt gap does not appear to close rapidly with chain length. For short-ranged interactions however, the Schmidt gap vanishes in a parameter region corresponding to an antiferromagnetic phase with gapless edge modes. These results demonstrate that the Schmidt gap can be used to distinguish quantum phases in the long-range Kitaev model.}, url = {http://paperview.spp-online.org/proceedings/article/view/107}, author = {Cleofe Dennielle P. Ayang-ang and Francis N. C. Paraan} } @article {376, title = {Simple techniques for improving deep neural network outcomes on commodity hardware}, journal = {AIP Conf. Proc. (8th Jagna International Workshop)}, volume = {1871}, year = {2017}, pages = {040001 }, abstract = {We benchmark improvements in the performance of deep neural networks (DNN) on the MNIST data test upon implementing two simple modifications to the algorithm that have little overhead computational cost. First is GPU parallelization on a commodity graphics card, and second is initializing the DNN with random orthogonal weight matrices prior to optimization. Eigenspectra analysis of the weight matrices reveal that the initially orthogonal matrices remain nearly orthogonal after training. The probability distributions from which these orthogonal matrices are drawn are also shown to significantly affect the performance of these deep neural networks.}, doi = {10.1063/1.4996523}, url = {http://aip.scitation.org/doi/10.1063/1.4996523}, author = {Nicholas Christopher A Colina and Carlos E Perez and Francis N. C. Paraan} } @conference {sambo2017, title = {Spin correlation functions of the ground-state quenched XY model}, year = {2017}, month = {24{\textendash}25 May 2017}, pages = {153}, publisher = {2nd International Science Graduate Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {We obtain exact expressions for the magnetizations and spin correlation functions for the ground-state quenched spin-1/2 XY model with both anisotropy and transverse magnetic field as quench parameters. The spin correlation functions were evaluated by Pfaffians of matrices with spinless fermionic operator correlations as elements. The transverse magnetization is obtained in the thermodynamic limit by the computation of a time-dependent density matrix. Non-analyticities in these quantities at some critical times are indicative of dynamical quantum phase transitions.}, author = {Jan Philippe B. Sambo and Francis N. C. Paraan} } @conference {375, title = {Spin-orbit coupled effects on the heat capacity of a two-dimensional electron gas}, year = {2017}, month = {4{\textendash}7 Jan 2017}, publisher = {8th Jagna International Workshop}, address = {Jagna, Bohol}, url = {https://www.msuiit.edu.ph/announcements/detail.php?id=1063}, author = {Cristine Villagonzalo} } @conference {430, title = {Strong chemisorption of CO on neutral B13 cluster edge site}, year = {2017}, month = {8{\textendash}11 Aug 2017}, pages = {PS-03}, publisher = {9th Conference of Asian Consortium on Computational Materials Science}, address = {Kuala Lumpur, Malaysia}, abstract = {We investigate the interaction of carbon monoxide (CO) molecule with neutral boron 13 (B13) cluster using spin-polarized density functional theory (DFT). We found that the edge sites of B13 cluster is the most reactive part, with strong CO adsorption of around -1.67 eV. Molecular orbitals analysis of the cluster shows that~the HOMO nearest to the Fermi level contributes to the adsorption of CO molecule. Our results indicate that~B13 cluster~could have potential applications in the storage and sequestration of CO molecules.}, url = {https://umconference.um.edu.my/accms-9}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @inproceedings {felismino, title = {Wigner functions and uncertainty products from partially transposed Dicke model ground states}, booktitle = {Proceedings of the 35th Samahang Pisika ng Pilipinas Physics Conference}, year = {2017}, month = {7{\textendash}10 June 2017}, pages = {SPP-2017-PB-03}, address = {Cebu City, Philippines}, abstract = {Wigner functions are used to calculate position-momentum uncertainty products from partially transposed Dicke model ground states that are partitioned into atomic and photonic degrees of freedom. No violations of the canonical minimum uncertainty relation are observed. However, the position-momentum uncertainty product is seen to diverge as a power law as the quantum critical coupling strength is approached.}, url = {http://paperview.spp-online.org/proceedings/article/view/69}, author = {John Ian Kenneth E. Felismino and Francis N. C. Paraan} } @inproceedings {333, title = {Benchmarking GPU acceleration of a parallel molecular dynamics simulation}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-19}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The parallel speedup of component subroutines in a molecular dynamics simulation is measured after implementing MPI-based CPU parallelization and GPU acceleration. GPU acceleration was observed to yield an order of magnitude reduction in simulation times (13.9x{\textendash}23.6x relative to a serial run). Slightly less speedup is achieved by CPU parallelization (7.5x) over nine processors. Performance scaling is diminished by communication operations as the number of processes launched begin to exceed the number of available physical CPU cores.}, author = {Zed Harold E. Fernandez and Lloyd Francis L Co and Francis N. C. Paraan} } @inproceedings {338, title = {Block entanglement in the ground state of the Majumdar-Ghosh model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-22}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We use matrix product state representations and transfer matrix methods to calculate the reduced density matrix of a block of spins in the ground state of the Majumdar-Ghosh spin chain. The full entanglement spectrum is obtained and the von Neumann entanglement entropy is expressed as a function of block length. We found that the von Neumann entropy increases exponentially fast as the length of the block increases and has a saturation value of Smax = ln 3.}, author = {Jade Farrah Dianne T Mendoza and Francis N. C. Paraan} } @conference {mendoza-qpcmp-2016, title = {Block entanglement in the Majumdar-Ghosh model ground state}, year = {2016}, month = {18{\textendash}19 Apr 2016}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/23-imsp-news/training-and-conference/386-quantum-phenomena-workshop}, author = {Jade Farrah Dianne Mendoza} } @inproceedings {316, title = {Clustering of irradiated cells due to the bystander effect}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, pages = {SPP-2016-1C-01}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {For quite some time, it has been observed that cells become irradiated despite the fact that no charged particle has ever directly traversed them. This is known as the radiation-induced bystander effect (RIBE). Because RIBE can be characterized as a Markov branching process, some degree of clustering can be expected to occur. By removing the influence of cell positioning on the formation of cancer clusters, we determine that alone, RIBE has a weak, yet non-negligible effect on cluster formation.}, author = {Eduard Renzo Santos and Cristine Villagonzalo} } @conference {340, title = {Dependence of Topological Anderson Insulator Phase on the Statistical Distribution of Disorder}, year = {2016}, month = {25{\textendash}27 Jan 2016}, pages = {P1-SC-003}, publisher = {Annual Meeting of the Physical Society of the Republic of China}, address = {National Sun Yat-sen University, Kaohsiung}, abstract = {We consider the dependence to statistical distribution of disorder for attaining disorder-induced topological Anderson insulator (TAI) phase characterized by quantized conductance plateau established in HgTe quantum well simulations. The renormalization of parameters that explains the transition from metal to TAI phase under the effective medium theory proposed by Groth et al. are proportional to the strength of disorder and not explicitly on its statistics. We then suppose that as long as the strength of disorder can be defined, under the appropriate conditions, the system will exhibit the TAI phase. We compare, for instance, the disorder drawn from Gaussian distribution to the case of disorder drawn from a uniform distribution where TAI phase is initially demonstrated. We found that the first case exhibits TAI phase but is not as robust as the uniform distribution case. Inspection of the Gaussian type of disorder is pursued due to vast observation of such distribution in nature. We consider as well the condition when the uniform distribution is discrete, as opposed to being continuous. Lastly, we discuss a possible generalization under the effective medium theory.}, url = {http://psroc2016.conf.tw}, author = {Gene Moses M Itable and Cristine Villagonzalo} } @article {374, title = {Detailed calculation of the average work done in a ground state quench of the quantum Ising model}, journal = {Science Diliman}, volume = {28:2}, year = {2016}, pages = {54-64}, abstract = {A detailed derivation of the exact expression for the average work done in a transverse field quench of the quantum Ising model ground state is presented. In the thermodynamic limit, it is proved that the average work done generally has inflection points at the critical field for the pre-quench quantum phase transition. The first divergent field derivative is calculated and is shown to diverge logarithmically. We also demonstrate that the average work done is equal to the product of the transverse magnetization of the pre-quench ground state and the change in the magnetic field.}, url = {http://www.journals.upd.edu.ph/index.php/sciencediliman/article/view/5509/4939}, author = {Salvador T Laurente Jr and Francis N. C. Paraan} } @conference {sambo-qpcmp-2016, title = {Dynamical quantum phase transition in the XY model}, year = {2016}, month = {18{\textendash}19 Apr 2016}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/23-imsp-news/training-and-conference/386-quantum-phenomena-workshop}, author = {Jan Philippe Sambo} } @inproceedings {336, title = {Edge states of the topological Anderson insulator}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-3A-04}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The disorder-induced topological Anderson insulator (TAI) has a similar characteristic to a topological insulator, i.e. insulator in the bulk but conductor in the boundary. In the framework of an effective medium theory, we show that at the transition to TAI from a weaker disorder regime, the conditions for the edge states to exist are appropriately changed yet the physics remains unaltered. This then led us to explore the behavior of edge states at the domain wall of a TAI and a non-TAI through numerical simulations.}, author = {Gene Moses M Itable and Cristine Villagonzalo} } @conference {372, title = {Entanglement and fluctuations in the Majumdar-Ghosh model ground state}, year = {2016}, month = {4{\textendash}8 Dec 2016}, pages = {QUICC S1}, publisher = {Joint 13th Asia Pacific Physics Conference and 22nd Australian Institute of Physics Congress}, address = {Brisbane, Australia}, abstract = {The matrix product state representation of the ground state of the Majumdar{\textendash}Ghosh Model (MGM) is used to obtain the reduced density matrix of a block of x spins in a periodic MGM chain. This calculation leads to exact expressions for the entanglement entropy and subsystem fluctuations as a function of block length. We find that the entanglement entropy saturates exponentially to ln 3, even as the subsystem Hilbert space is five-dimensional.}, url = {http://aappsbulletin.org/myboard/read.php?Board=others\&id=100}, author = {Jade Farrah Dianne Mendoza and Francis N. C. Paraan} } @inproceedings {335, title = {Entanglement and ground state level crossings in an extended Hubbard dimer}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-20}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The single-site entanglement entropy in the ground state of an extended Hubbard dimer is calculated in terms of intrasite and intersite interaction parameters. Entanglement vanishes in a ferromagnetic regime characterized by a degenerate spin-polarized ground state. In parameter ranges with non-zero entanglement, the ground state is a linear combination of states with spin and charge modulation.}, author = {Robertson C. Esperanza and Francis N. C. Paraan} } @article {330, title = {Entanglement-fluctuation relation for bipartite pure states}, journal = {Phys. Rev. A}, volume = {94}, year = {2016}, pages = {022323}, abstract = {We identify subsystem fluctuations (variances) that measure entanglement in an arbitrary bipartite pure state. These fluctuations are of observables that generalize the notion of polarization to an arbitrary N-level subsystem. We express this polarization fluctuation in terms of subsystem purity and other entanglement measures. The derived entanglement-fluctuation relation is evaluated for the ground states of a one-dimensional free-fermion gas and the Affleck-Kennedy-Lieb-Tasaki spin chain. Our results provide a framework for experimentally measuring entanglement using Stern-Gerlach{\textendash}type state selectors.}, doi = {10.1103/PhysRevA.94.022323}, url = {http://link.aps.org/doi/10.1103/PhysRevA.94.022323}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @inproceedings {334, title = {Genetic diversity in a Penna model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-20}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We considered genetic diversity within the framework of the Penna model. Using the entropy of genetic diversity as measure, we found genetic diversity to increase with reproductive age R, for the case where the threshold parameter T is less than R. In addition, we found the saturation population to decrease with increasing genetic diversity.}, author = {Amancio II Manceras and Ronald Banzon} } @inproceedings {313, title = {Importance of initialization of weight matrices in deep learning neural networks}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-21}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The success of deep neural networks relies on optimized weight matrices are initialized in different ways. This work reports learning improvement in a six-layer deep neural network that is initialized with orthogonal weight matrices when compared to other commonly-used initialization schemes. An analysis of the eigenvalue spectra of the optimized solutions implies that the space of orthogonal weight matrices lies close to the manifold of learned states.}, author = {Nicholas Christopher A Colina and Carlos E Perez and Francis N. C. Paraan} } @article {165, title = {Integer effects in the entanglement and spin fluctuations of a quantum Hall system with Rashba interactions}, journal = {J. Stat. Mech. Theor. Exp.}, volume = {2016}, year = {2016}, pages = {053104}, abstract = {

We report distinctive nonanalytic signatures in the spin{\textendash}orbit entanglement of a 2D electron gas with Rashba interactions at integer values of the filling factor and at certain level crossings. The accompanying sharp changes in the bulk spin{\textendash}orbit entanglement entropy can be probed by measuring the fluctuation in the transverse spin polarization of the electron gas.

}, doi = {10.1088/1742-5468/2016/05/053104}, author = {Rona F Barbarona and Francis N. C. Paraan} } @inproceedings {309, title = {Investigation of neutral B13 clusters: A density functional theory study}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-18}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We investigate the electronic structure of neutral boron_13 (B13) clusters using spin-polarized density functional theory (DFT). The stable B13 cluster is observed to have a two-dimensional planar structure. Energy levels diagram shows that it has a highest occupied molecular orbital{\textendash}lowest unoccupied molecular orbital (HOMO-LUMO) gap of 0.36 eV. Analysis of the electronic charge density of the B13 cluster reveals that most of the electrons are shared between B atoms and are located at the edges, where the HOMO and LUMO are also localized. Our results indicate that the most reactive part of the cluster is along its edges.}, author = {Alexandra B. Santos-Putungan and Nata{\v s}a Stoji{\'c} and Nadia Binggeli and Francis N. C. Paraan} } @inproceedings {337, title = {k{\textperiodcentered}p Perturbation Model of the Three-terminal Ferromagnet-Insulator-Semiconductor Device with Spin-Orbit Interaction}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-17}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Although the creation of spin polarization in semiconductors in a three-terminal ferromagnet-insulator-normal conductor (3T-FIN) proved successful experimentally, the behavior of spin carriers are not yet well understood. Here we develop a model based on the k{\textperiodcentered}p perturbation theory to provide an insight to the energy behavior of spin carriers in the semiconductor. A potential barrier and with a half-harmonic oscillator model was utilized. It was established that for the model potential, the spin-orbit interaction does not contribute to the additional energy in the 3T-FIN device for both polarized and unpolarized input.}, author = {April Cortez and Cristine Villagonzalo} } @inproceedings {332, title = {Loschmidt amplitude zeros as a probe for criticality in the quenched XY model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5C-06}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {This paper investigates the correspondence between dynamical phase transitions (DPT) and quenches across quantum critical points (QCP) in ground state quenches of a spin-1/2 XY model. These DPTs are identified by treating the wavefunction overlap between pre- and post-quench states as a partition funtion and determining its Fisher zeros. It is found that DPTs do not always occur when the quench crosses a quantum critical line. A general condition for the occurrence of these DPTs in the XY model is derived.}, author = {Jan Philippe B. Sambo and Francis N. C. Paraan} } @inproceedings {322, title = {Molecular dynamics of rapid melting in a copper-silver alloy}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PA-22}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {A copper-silver alloy (64\% Cu / 36\% Ag atomic ratio) is simulated by molecular dynamics. The alloy is subjected to rapid linear heating protocols from room temperature to 2100 K at several ramp rates of the order ~K/ps. Numerical evidence for a first-order melting transition at 1.19 x 10^3 K is observed. This elevated value is suggested to be the result of high pressures in the microscopic sample.}, author = {Cleofe Dennielle P. Ayang-ang and John Joseph S Solo and Zed Harold E. Fernandez and Francis N. C. Paraan} } @inproceedings {311, title = {Molecular dynamics simulation of liquid gallium using an embedded atom model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5B-03}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Optimized embedded atom model (EAM) potential parameters from the literature are used to perform a molecular dynamics simulation of liquid gallium. Liquid densities are calculated at several temperatures at a fixed pressure of 1 atm to determine the mean coefficient of thermal expansion. Radial pair distribution functions showing the shell structure of the liquid phase are also obtained and compared with previous simulations and experimental results.}, author = {Oliver B. Generalao and Allan Jay Pari{\~n}as and Francis N. C. Paraan} } @conference {339, title = {A Multi-functional Spintronic Device Driven by Spin-orbit Interactions}, year = {2016}, month = {25{\textendash}27 Jan 2016}, pages = {O3-NP1 01}, publisher = {Annual Meeting of the Physical Society of the Republic of China}, address = {National Sun Yat-sen University, Kaohsiung}, abstract = {We propose a simple two-terminal device that operates simultaneously as (i) a spin inverter for an incident polarized electron, (ii) a spin polarizer for an unpolarized source and (iii) a tunable spin current attenuator at certain range of electron energies. The device consists of a U-shaped nanowire with a uniform Dresselhaus spin-orbit coupling and a spatially-modulated Rashba spin-orbit coupling along the curved section. The latter is implemented through a tunable gate voltage at every alternating segment along the wire{\textquoteright}s arc. This multi-purpose device does not need magnetic components or an external magnetic field to carry out the different functions as enumerated above. We discuss how the interplay of the wire{\textquoteright}s geometry and the spin-orbit interaction present in the device drives its spin transport.}, url = {http://psroc2016.conf.tw}, author = {Carlos Baldo III and Cristine Villagonzalo} } @inproceedings {314, title = {Multispecies fluid flow simulations inside a chamber via computational fluid dynamics}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-2C-04}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {Computational fluid dynamics simulations of silane inside a two-dimensional container filled with nitrogen gas were performed using finite element methods. Pressure gradients were introduced to the system, and the time needed for the system to reach dynamic equilibrium for mass fractions, pressure, and velocity was determined. The inlet size was also varied to determine how it affects the equilibriation time.}, author = {Apolinario Miguel I. Tan and Nicholas Christopher A Colina and Jennifer Anne Constantino and Francis N. C. Paraan} } @inproceedings {312, title = {Near-resonant approximation in quantum search simulation}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-2C-01}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {
The simulation of a quantum search algorithm in an Ising spin chain is equivalent to solving a system of 2^L coupled first order differential equations with L being the number of qubits. The near-resonant approximation can be used to simplify the evolution of the states in the database. In this work, we compare the simulation of a quantum search algorithm using the exact evolution according to Schr{\"o}dinger equation and using the near-resonant approximation. Our results show that the error of the near-resonant approximation is comparable to that of the exact evolution in terms of the fidelity measure. The advantage gained in having this small error at the near-resonant approximation is its faster execution time relative to the exact case.
}, author = {Neris D Ilano and Ronald Banzon and Cristine Villagonzalo} } @inproceedings {spvm-2016-1, title = {Observation of the behavior and properties of the critical micelle concentration (CMC) at different temperatures}, booktitle = {Proceedings of the 18th Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2016}, month = {20{\textendash}22 Oct 2016}, pages = {13}, address = {Silliman University, Dumaguete City}, author = {Allan Jay L Pari{\~n}as and John Joseph S Solo and Lloyd Francis L Co and Francis N. C. Paraan} } @inproceedings {310, title = {Parallelization benchmarks of plane wave self-consistent field calculations on an IBM BlueGene supercomputer}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-PB-19}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {A plane wave self-consistent field calculation was parallelized over two node cards of an IBM BlueGene/P supercomputer. A maximum speedup of 9x was measured in Virtual Node execution mode. The observed performance improvements are consistent with Amdahl{\textquoteright}s law for an algorithm that is approximately 89\% parallelizable.}, author = {Paul Daniel S. Ang and Lean Louiel A Peria and Joshua Gregor A Dizon and Francis N. C. Paraan} } @inproceedings {331, title = {Piezomagnetic properties and band structure of Mn3GaN calculated using density functional theory}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-3A-06}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {The antiperovskite Mn3GaN in the Γ-5g configuration has a noncollinear magnetic ordering and exhibits the piezomagnetic effect. This study aims to replicate previous ab initio studies of Mn3GaN. Magnetic moments are allowed to relax after applying various amounts of strain. Results show that the total magnetization varies linearly with strain up to {\textpm}2\%. The observed response of the magnetization was stronger for negative strain than for positive strain. Calculations reveal that this net magnetization arises from the strain-induced rotation of the local magnetic moments associated with each Mn atom. In addition, numerical calculations of the band structure and density of states of Mn3GaN are presented.}, author = {Lean Louiel A Peria and Paul Daniel S. Ang and Francis N. C. Paraan} } @conference {351, title = {Polarization fluctuation as an entanglement measure for N-level systems}, year = {2016}, month = {7{\textendash}8 Apr 2016}, pages = {127}, publisher = {1st International DOST-SEI ASTHRDP-NSC Scholars{\textquoteright} Conference}, address = {PICC, Pasay City}, abstract = {It is known that subsystem fluctuations are related to entanglement for any N-level system entangled with an environment. We define an observable wherein its fluctuations can be directly related to known measures such as the purity, R{\'e}nyi-2 entropy, and concurrence. This quantity, which we call the Schmidt polarization fluctuation shows an exact relationship between fluctuations and entanglement that is simple to construct and is model-independent. It can also be considered as a proper entanglement measure and is experimentally accessible.}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @conference {325, title = {Quantum criticality in a quenched XY chain}, year = {2016}, month = {25{\textendash}27 Jul 2016}, publisher = {Conference on Entanglement and Non-Equilibrium Physics of Pure and Disordered Systems}, address = {International Centre for Theoretical Physics, Trieste}, url = {http://indico.ictp.it/event/7604/}, author = {Francis A Bayocboc Jr and Jan Philippe Sambo and Francis N. C. Paraan} } @conference {paraan-qpcmp-2016, title = {Quenched spin chains and generalized Gibbs ensembles}, year = {2016}, month = {18{\textendash}19 Apr 2016}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/23-imsp-news/training-and-conference/386-quantum-phenomena-workshop}, author = {Francis N. C. Paraan} } @article {baldo2016a, title = {Spin inverter and polarizer curved nanowire driven by Rashba and Dresselhaus spin-orbit interactions}, journal = {Physica E}, volume = {83}, year = {2016}, note = {cited By 0; Article in Press}, pages = {498-504}, abstract = {
We propose in theory a curved nanowire structure that can both serve as a spin inverter and a spin polarizer driven by a periodic Rashba spin{\textendash}orbit coupling (SOC) and a uniform Dresselhaus SOC. The curved section of the U-shaped quasi-one dimensional nanowire with an arc of radius R and circumferential length πR is divided into segments of equal length initially having only its inherent homogeneous Dresselhaus SOC. Then a Rashba-type SOC is applied at every alternating segment. By tuning the Rashba SOC strength and the incident electron energy, this device can flip the spin at the output of an incoming spin-polarized electron. On the other hand, this same device acts as a spin filter for an unpolarized input for which an outgoing electron with a non-zero polarization can be achieved without the application of an external magnetic field. Moreover, the potential modulation caused by the periodic Rashba SOC enables this device to function as an attenuator for a certain range of incident electron energies that can make the probability current density drop to 10^(-4) of its otherwise magnitude in other regimes.
}, doi = {10.1016/j.physe.2015.11.024}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {spvm-2016-2, title = {Structural analysis and visualization of spatial distribution of electrons of pristine and alkali metal-doped polythiophene}, booktitle = {Proceedings of the 18th Samahang Pisika ng Visayas at Mindanao National Physics Conference}, year = {2016}, month = {20{\textendash}22 Oct 2016}, pages = {23}, address = {Silliman University, Dumaguete City}, author = {Prudence Peace V Bustamante and Melchor J Potestas and Francis N. C. Paraan} } @inproceedings {315, title = {Threshold carrying capacity for competing populations in a Penna model}, booktitle = {Proceedings of the 34th Samahang Pisika ng Pilipinas Physics Congress}, year = {2016}, month = {18{\textendash}21 Aug 2016}, pages = {SPP-2016-5C-05}, address = {University of the Philippines Visayas, Iloilo City}, abstract = {We consider two types of Penna model populations: VA, where the Verhulst factor is applied to the entire population, and VB, for which Verhulst is applied to newborns only. Resources are shared by summing both populations during coevolution. We determined a relative threshold carrying capacity for VB that still drives VA to extinction.}, author = {Christopher Patrick P. Elegado and Ronald Banzon} } @conference {itable-qpcmp-2016, title = {Which disorder distribution can induce an edge state in a HgTe quantum well?}, year = {2016}, month = {18{\textendash}19 Apr 2016}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/23-imsp-news/training-and-conference/386-quantum-phenomena-workshop}, author = {Gene M Itable} } @conference {371, title = {Zeros of the Loschmidt amplitude in the quenched XY model}, year = {2016}, month = {4{\textendash}8 Dec 2016}, pages = {CSCMP 48}, publisher = {Joint 13th Asia Pacific Physics Conference and 22nd Australian Institute of Physics Congress}, address = {Brisbane, Australia}, abstract = {We investigate the notion of dynamical quantum phase transitions (DQPTs) in the quenched ground state of the spin-1/2 XY model H(h0, γ0) to H(h1, γ1). By a Wick rotation, the Loschmidt amplitude is formally treated as a canonical partition function and its zeros used as a probe for criticality. This approach is similar to that used in a Fisher zero analysis in identifying classical phase transitions. The occurrence of real-time zeros for the Loschmidt amplitude signify DQPTs. Previously, a correspondence between DQPTs and quenches across critical points was observed for the transverse-field Ising model. The zeros of the Loschmidt amplitude in a quench of the XY model ground state was calculated and the corresponding condition for a DPQT to occur was derived for a generic quench. It can be observed that not all quenches across critical points are accompanied by DQPTs and vice versa. This result is consistent with previous studies of the quenched XY model.}, url = {http://aappsbulletin.org/myboard/read.php?Board=others\&id=100}, author = {Jan Philippe Sambo and Francis N. C. Paraan} } @conference {santos-putungan-qpcmp-2015, title = {Computational materials science via density functional theory: General introduction and success stories}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {Alexandra B. Santos-Putungan} } @inproceedings {320, title = {A critically damped quantum search may not necessarily be optimal}, booktitle = {Proceedings of the AQIS Conference 2015}, year = {2015}, month = {24{\textendash}30 Aug 2015}, pages = {147-148}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {We explore the rate at which the target state is obtained in a damped quantum search of an Ising system. As the number of target states is reduced, the damped quantum search gives a higher probability of success than that of the classical search. For any system in general, a new damping parameter was obtained from an optimization of the damped quantum search. Application of the optimum damping parameter per iteration on the damped quantum search shows a significant improvement of the probability of success over the critically damped quantum search.}, url = {http://aqis-conf.org/2015/program/}, author = {Neris D Ilano and Ronald Banzon and Cristine Villagonzalo} } @conference {350, title = {Effect of varying the position of the ancilla qubit and the coupling constants in the simulation of Grover{\textquoteright}s quantum search algorithm}, year = {2015}, month = {7{\textendash}11 Jan 2015}, pages = {P-62}, publisher = {9th International Conference on Computational Physics}, address = {National University of Singapore}, abstract = {We simulate Grover{\textquoteright}s algorithm in an Ising spin chain quantum computer with spatially-dependent coupling constant. The interaction to the nearest and second-nearest neighbor of the spins is considered. The behavior of the fidelity as a function of the number of Grover iteration during the algorithm is determined. For a fixed location of the ancilla qubit, the overall fidelity decreases as we increase the size of the database. Also, as we vary the coupling constant per neighbor, we obtain a high fidelity for a given number of iteration. The simulation of the algorithm using a classical computer system restricts the size of the database that gives a high fidelity result.}, url = {http://www.physics.nus.edu.sg/iccp9/}, author = {Neris D Ilano and Cristine Villagonzalo and Ronald Banzon} } @article {Seroje2015, title = {Effective thermodynamics of isolated entangled squeezed and coherent states}, journal = {Eur. J. Phys.}, volume = {36}, number = {5}, year = {2015}, pages = {055051}, abstract = {The R{\'e}nyi entanglement entropy is calculated exactly for mode-partitioned isolated systems such as the two-mode squeezed state and the multi-mode Silbey{\textendash}Harris polaron ansatz state. Effective thermodynamic descriptions of the correlated partitions are constructed to present quantum information theory concepts in the language of thermodynamics. Boltzmann weights are obtained from the entanglement spectrum by deriving the exact relationship between an effective temperature and the physical entanglement parameters. The partition function of the resulting effective thermal theory can be obtained directly from the single-copy entanglement.}, doi = {10.1088/0143-0807/36/5/055051}, author = {King Karl R Seroje and Rafael S. dela Rosa and Francis N. C. Paraan} } @inproceedings {cortez-spp-2015, title = {Electric field and spin precession effects on spin injection to semiconductors in three-terminal ferromagnet-insulator-nonmagnetic junctions}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PA-44}, address = {University of Northern Philippines, Vigan City}, abstract = {
The application of an electric field and the ensuing spin precession due to internal magnetic fields in the semiconductor of a three-terminal (3T) device is investigated using the standard diffusion theory. Because the externally applied current is confined in one direction in such a device, the effective electric field is assumed to be significant. The dominant precession direction that dictates the spin dynamics is perpendicular to both the injected spins and the electric field. At large effective electric fields, the polarization in the semiconductor is completely drawn from the polarization of the ferromagnet and becomes well-distributed in the semiconductor.
}, author = {April Cortez and Cristine Villagonzalo} } @conference {cortez-qpcmp-2015, title = {Electric field and spin precession effects on spin injection to semiconductors in three-terminal ferromagnet-insulator-nonmagnetic junctions}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {April Cortez} } @inproceedings {baldo-spp-2015, title = {Electron spin polarization along a one-dimensional wire with periodic Rashba and uniform Dresselhaus spin-orbit couplings}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-3B-05}, address = {University of Northern Philippines, Vigan City}, abstract = {
We investigate the transmission of an electron spin on a one-dimensional wire with a periodic Rashba spin-orbit couplings (SOC) and a constant contribution from a Dresselhaus SOC. The straight wire is divided into initially uniform segments and the Rashba SOC is turned on every alternating segment. Eigenvalues and eigenfunctions for both without and with Rashba SOC segments are analytically derived. From these obtained values, we numerically calculate the net polarization at the output. We find in our result that regardless of the initial spin orientation, the output polarization turns out to be spin-up polarized. The modulation effect of the segment length of the wire via a periodic Rashba SOC is manifested by the appearance of an energy gap whose width increases with larger Rashba coupling strength. On the other hand, the position of the gap can be tuned by setting the strength of the Dresselhaus SOC. We find that for electrons with Fermi energies falling within this gap, the output spin current is unpolarized.
}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {santosputungan-spp-2015, title = {Enhanced ferromagnetism in Zn0.5 (Co)0.5 O alloy: DFT calculations}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PA-14}, address = {University of Northern Philippines, Vigan City}, abstract = {
In this work, we studied the structure and magnetic properties of Zn0.5(Co)0.5O alloy via spin-polarized density functional theory DFT. We utilized a 1 x 1 ZnO hexagonal wurtzite unit cell in a 4-atom bilayer configuration, with one Zn atom replaced by a Co atom. We found that the original lattice parameters of ZnO did not change appreciably upon Co alloying, and thus the structure remains robust. Similarly, minimal charge redistribution between the metals and oxygen is observed. Lastly, our calculations showed that the net magnetization of ZnO upon Co alloying is enhance significantly, much larger than that via doping. The results suggest that\ Zn0.5(Co)0.5O\ as a ferromagnetic material is a potential candidate for advanced spintronic applications.
}, author = {Alexandra B. Santos-Putungan and Joshua Gregor A Dizon and Darwin B Putungan and Francis N. C. Paraan} } @inproceedings {delarosa-spp-2015, title = {Entanglement entropy of the Silbey-Harris polaron ansatz for a spin-boson model}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PB-47}, address = {University of Northern Philippines, Vigan City}, abstract = {
We obtained the entanglement entropy between a qubit and a harmonic oscillator bath using a Silbey-Harris polaron ansatz. With the assumption that a single mode frequency is dominant, we calculated the exact dependence of the von Neumann entropy on the displacement parameter. The entanglement entropy increases and saturates exponentially fast to its maximum value of ln2 as the magnitude of the displacement increases. We also showed that the entanglement entropy depends on the sum of complex squares of each displacement when the bath is a multi-mode coherent state.
}, author = {Rafael S. dela Rosa and Francis N. C. Paraan} } @inproceedings {laurente-spp-2015, title = {Exact calculation of the average work done in a quenched quantum Ising model}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PB-48}, address = {University of Northern Philippines, Vigan City}, abstract = {
The main aim of this paper is to calculate the average work done in a ground state quench of the XY Heisenberg model in the transverse field quantum Ising limit. We obtain an exact closed form expression for the average work done in terms of complete elliptic integrals. This result reveals an inflection point at a pre-quench field that satisfies |h0|=1, which signals quantum criticality.
}, author = {Salvador T Laurente Jr and Francis N. C. Paraan} } @inproceedings {bayocboc-spp-2015, title = {Exact expression for the work fluctuation in a quenched transverse field Ising chain}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-PA-48}, address = {University of Northern Philippines, Vigan City}, abstract = {
We study the emergent thermodynamics associated with an arbitrary field quench in the Transverse Field Ising Model by calculating the fluctuations in the work done. An exact expression for the work fluctuation is obtained and is shown to exhibit non-analytic behavior when the system is initially critical.
}, author = {Francis A Bayocboc Jr and Francis N. C. Paraan} } @article {Bayocboc2015, title = {Exact work statistics of quantum quenches in the anisotropic XY model}, journal = {Phys. Rev. E}, volume = {92}, number = {3}, year = {2015}, pages = {032142}, abstract = {We derive exact analytic expressions for the average work done and work fluctuations in instantaneous quenches of the ground and thermal states of a one-dimensional anisotropic XY model. The average work and a quantum fluctuation relation is used to determine the amount of irreversible entropy produced during the quench, eventually revealing how the closing of the excitation gap leads to increased dissipated work. The work fluctuation is calculated and shown to exhibit nonanalytic behavior as the prequench anisotropy parameter and transverse field are tuned across quantum critical points. Exact compact formulas for the average work and work fluctuation in ground state quenches of the transverse field Ising model allow us to calculate the first singular field derivative at the critical field values.}, doi = {10.1103/PhysRevE.92.032142}, author = {Francis A Bayocboc Jr and Francis N. C. Paraan} } @inproceedings {tacbad-spp-2015, title = {Lateral motion of a spherical particle suspended in Couette flow}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-5C-04}, address = {University of Northern Philippines, Vigan City}, abstract = {
This study aims to simulate the lateral motion of a neutrally buoyant spherical particle suspended in Couette flow using a lattice-Boltzmann algorithm. It was found that the particle migrates to an equilibrium position at the center of the channel regardless of its initial position. A force coupling constant controls the strength of particle and fluid interactions. Requiring this constant to enforce Stokes{\textquoteright} drag on the particle resulted in a slightly faster migration than when using a constant that conserves the net kinetic energy.
}, author = {Robert C Tacbad and Zed Harold E. Fernandez and Francis N. C. Paraan} } @conference {paraan-qpcmp-2015, title = {Mode entanglement in BCS superconductivity, quantum optics, and quantum Hall physics}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {Francis N. C. Paraan} } @inproceedings {itable-spp-2015, title = {Non-equilibrium collective transport in an Ising chain with Kawasaki dynamics}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-5C-03}, address = {University of Northern Philippines, Vigan City}, abstract = {
An Ising chain with Kawasaki spin-exchange dynamics in contact with a heat bath with temporal periodic variation between two temperatures is considered. This environment prohibits the system from attaining thermal equilibrium. We demonstrate here via Monte Carlo simulations that such a case exhibits a Brownian motor type collective transport. This confirms our hypothesis that a cycle of cluster and dispersion of domains with fine tuned parameters, in effect, results into spin transport.
}, author = {Gene Moses M Itable and Cristine Villagonzalo} } @conference {349, title = {Optimal curvilinear transport of a spin-polarized electron with Rashba and Dresselhaus spin-orbit coupling in a uniform magnetic field}, year = {2015}, month = {7{\textendash}11 Jan 2015}, pages = {C3-13}, publisher = {9th International Conference on Computational Physics}, address = {National University of Singapore}, abstract = {The spin-polarized transport of an electron along a curved-one dimensional wire with Rashba and Dresselhaus spin-orbit couplings (SOCs) and a uniform perpendicular magnetic field is considered in this study. Here we analytically derived the appropriate eigenenergies and eigenvalues of the system and numerically determine the output transmission coefficients. Spin polarization, probability current density and conductance are then obtained using transfer matrix approach to examine the dependence of spin transport on the radius, R, of curved wire, on the external magnetic field, B, and on the SOCs strengths.
From our results, we find the condition, B ≈ R^(1/3), at which there would be no spin switching regardless of the SOC strengths. A value of R beyond this condition will no longer have a spin reversal. Moreover, for a material with sufficiently strong SOCs, regardless of its type, the effect of the external magnetic field is reduced. The effective SOC strength follows the standard form equation of a circle in which the Rashba SOC and the Dresselhaus SOC are the component coordinates. From here, we optimize the probability current density by properly tuning the Rashba coupling strength for a given value of B, R and Dresselhaus SOC.}, url = {http://www.physics.nus.edu.sg/iccp9/}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {321, title = {Polarization fluctuation as an entanglement monotone for entangled two-level systems}, booktitle = {Proceedings of the AQIS Conference 2015}, year = {2015}, month = {24{\textendash}30 Aug 2015}, pages = {271-272}, address = {Korea Institute for Advanced Study, Seoul}, abstract = {In a pure system consisting of a two-level atom (qubit) entangled with an arbitrary environment, the polarization fluctuation about the Schmidt axis is shown to preserve majorization. This polarization fluctuation is additive over independent two-level systems and is proposed to be an experimentally accessible entanglement monotone for a generic gas of two-level atoms entangled with a common bath.}, url = {http://aqis-conf.org/2015/program/}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @inproceedings {villaruel-spp-2015, title = {Polarization fluctuation can partially order entangled qubit states}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-3B-03}, address = {University of Northern Philippines, Vigan City}, abstract = {
We define and calculate the Schmidt polarization fluctuation of a qubit entangled with an arbitrary environment in a bipartite pure state. It is found that this polarization fluctuation preserves majorization and thus can partially order qubits. We propose that this quantity can be used as an experimentally accessible entanglement measure.
}, author = {Aura Mae B Villaruel and Francis N. C. Paraan} } @conference {villaruel-qpcmp-2015, title = {Quantum fluctuation theorems in quenched systems}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {Aura Mae Villaruel} } @inproceedings {puspus-spp-2015, title = {R{\'e}nyi entanglement entropy of the spin-partitioned BCS ground state}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {spp-2015-2B-03}, address = {University of Northern Philippines, Vigan City}, abstract = {
We use the R{\'e}nyi entanglement entropy to study entanglement between the spin components of the Bardeen-Cooper-Schrieffer (BCS) ground state and we characterize its limiting values. We show that R{\'e}nyi entropies peak in the region about the Fermi surface. We also show that the orbital single-copy entanglement can be interpreted as the thermodynamic free energy of a two-level system at thermal equilibrium. We observed that the total R{\'e}nyi-2 entropy and the total single-copy entanglement are proportional to the number of electron orbitals having energies about the Fermi energy.
}, author = {Xavier M Puspus and Francis N. C. Paraan} } @inproceedings {ilano-spp-2015, title = {Simulation of Grover{\textquoteright}s algorithm with position-variation of the ancilla qubit}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-2B-06}, address = {University of Northern Philippines, Vigan City}, abstract = {
We simulate Grover{\textquoteright}s quantum search algorithm in an Ising spin chain quantum computer with nearest and second-nearest neighbor interactions. We determine the optimum Rabi frequency that satisfies the 2πk method by selecting a high fidelity value in the frequency scan for each database size. Also, we vary the position of the ancilla qubit and investigate the effect on the fidelity for different sizes of the database. The behavior of the fidelity as a function of the number of Grover iterations during the algorithm is considered. For a fixed location of the ancilla qubit, the overall fidelity decreases as we increase the size of the database.
}, author = {Neris D Ilano and Ronald S. Banzon and Cristine Villagonzalo} } @conference {ilano-qpcmp-2015, title = {Simulation of the quantum search algorithm in an Ising spin system}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {Neris D Ilano} } @conference {villagonzalo-qpcmp-2015, title = {Spectral and thermodynamic properties of two-dimensional electron systems in the quantum Hall regime}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {Cristine Villagonzalo} } @inproceedings {barbarona-spp-2015, title = {Spin polarization and its fluctuation in a two-dimensional electron gas with Rashba spin-orbit interactions}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-5C-07}, address = {University of Northern Philippines, Vigan City}, abstract = {
The total spin polarization of a two-dimensional gas in the presence of a transverse magnetic field and Rashba spin-orbit interaction vanishes at high filling factors (weak magnetic fields) and shows the location of level crossings at sudden changes in its values. At strong magnetic fields, non-analyticities in the behavior of the spin fluctuations are exhibited at half-integer filling factors.
}, author = {Rona F Barbarona and Francis N. C. Paraan} } @conference {baldo-qpcmp-2015, title = {Spin switching in a spin-orbit coupled transport in a curved nanowire}, year = {2015}, month = {22{\textendash}23 Apr 2015}, publisher = {Workshop on Theories in Quantum Phenomena and Condensed Matter Physics}, address = {University of the Philippines Los Ba{\~n}os, Laguna}, url = {https://imsp.uplb.edu.ph/index.php/component/content/article/17-imsp-news/research/370-workshop-on-theories-in-quantum-phenomena-and-condensed-matter-physics}, author = {Carlos F Baldo III} } @conference {352, title = {Structural and magnetic properties of Zn0.5 Co0.5 O alloy configurations via DFT}, year = {2015}, month = {16{\textendash}18 June 2015}, pages = {56}, publisher = {8th Conference of Asian Consortium on Computational Materials Science}, address = {National Taiwan University of Science and Technology, Taipei}, abstract = {We studied the structure and magnetic properties of ZnCoO alloy configurations via spin-polarized density functional theory (DFT). For the hexagonal wurtzite Zn0.5(Co)0.5O alloy, we used a 1x1x1 ZnO unit cell in a 4-atom bilayer configuration, with one Zn atom replaced by Co. In a similar manner, we utilized a 1x1x1 CoO rocksalt structure, with four Co atoms replaced by Zn to obtain Co0.5(Zn)0.5O. We found that the original ZnO lattice did not change appreciably upon Co alloying, with around 2\% compression, and thus the structure remains robust and atoms bond stronger. This is complemented by Zn0.5(Co)0.5O stronger bulk cohesive energy per formula unit (8.29 eV) compared to bulk ZnO (7.05 eV). Additionally, minimal charge redistribution between the metal atoms and oxygen is observed. On another note, a volume expansion of 3\% was observed for Co0.5(Zn)0.5O, implying the formation of weaker bonds between atoms. The calculated bulk cohesive energy per formula unit for CoO is 9.47 eV, quite larger than that of Co0.5(Zn)0.5O at 8.07 eV. Lastly, our calculations showed that the net magnetization of ZnO upon Co alloying is enhanced significantly, while the reverse is true for Zn-alloyed CoO. The results suggest that Zn0.5(Co)0.5O is more stable in hexagonal wurtzite structure and could be a better controllable ferromagnetic material for spintronics applications.}, url = {http://www.iams.sinica.edu.tw/accms8/program$\#$poster}, author = {Alexandra B. Santos-Putungan and Francis N. C. Paraan} } @inproceedings {salazar-spp-2015, title = {Structural and optical properties of ZnO microrods as fast and efficient UV scintillator materials}, booktitle = {Proceedings of the 33rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2015}, month = {3{\textendash}6 Jun 2015}, pages = {SPP-2015-5B-07}, address = {University of Northern Philippines, Vigan City}, abstract = {
Aqueous chemical grown zinc oxide (ZnO) microrods are found to be crystalline, uniform and well-faceted in terms of structure and morphology. From photoluminescence spectroscopy, these microrods interestingly exhibit ultraviolet (UV) near-band-edge emission at 392 nm (3.16 eV) without any visible or defect-related emission. The UV emission also intensifies with increasing excitation energy. Spectral narrowing is not observed indicating the non-existence of lasing nor stimulated emission from these structures. Having fast luminescence lifetimes less than 100 ps, these ZnO microrods then hold a promise as potential candidates for fast and effcient scintillator materials.
}, author = {Hernanie T Salazar Jr and Alexandra B. Santos-Putungan and Arnel A Salvador and Roland V Sarmago and Melvin John F Empizo and Kohei Yamanoi and Ren Arita and Toshihiko Shimizu and Nobuhiko Sarukura} } @conference {353, title = {Work statistics in quantum quenches in the Heisenberg XY model}, year = {2015}, month = {9{\textendash}13 Mar 2015}, publisher = {Quantum many-body systems far from equilibrium: Quench dynamics, thermalisation, and cold-atom experiments}, address = {National Institute for Theoretical Physics, Stellenbosch}, url = {http://www.nithep.ac.za/4i5.htm}, author = {Francis A Bayocboc Jr and Francis N. C. Paraan} } @article {Puspus2014, title = {Entanglement spectrum and number fluctuations in the spin-partitioned BCS ground state}, journal = {Phys. Rev. B}, volume = {90}, number = {15}, year = {2014}, note = {cited By 2}, pages = {155123}, abstract = {
We study entanglement between the spin components of the BCS ground state by calculating the full entanglement spectrum and the corresponding von Neumann entanglement entropy. The entanglement spectrum is effectively modeled by a generalized Gibbs ensemble (GGE) of noninteracting electrons, which may be approximated by a canonical ensemble at the BCS critical temperature. We further demonstrate that the entanglement entropy is jointly proportional to the pairing energy and to the number of electrons about the Fermi surface (an area law). Furthermore, the entanglement entropy is also proportional to the number fluctuations of either spin component in the BCS state.
}, doi = {10.1103/PhysRevB.90.155123}, author = {Xavier M Puspus and Kristian Hauser Villegas and Francis N. C. Paraan} } @conference {355, title = {Fundamental studies and simulation of nanostructured materials}, year = {2014}, month = {13{\textendash}15 Feb 2014}, publisher = {6th Asian Computational Materials Design Workshop}, address = {De La Salle University, Manila}, url = {http://cmdasiaphilippines.wixsite.com/cmd-asia/6th-cmd-programme-day-1}, author = {Cristine Villagonzalo} } @inproceedings {324, title = {Integer effects in the spin-orbit entanglement entropy in a 2D electron system with Rashba interactions}, booktitle = {Proceedings of the AQIS Conference 2014}, year = {2014}, month = {20{\textendash}24 Aug 2014}, pages = {239-240}, address = {Kyoto University, Japan}, abstract = {The entanglement between spin and orbital degrees of freedom in a two-dimensional electron system with Rashba spin-orbit coupling displays non-analytic behavior at integer filling factors.}, url = {http://aqis-conf.org/2014/program/}, author = {Rona F Barbarona and Francis N. C. Paraan} } @inproceedings {tacbad-spp-2014, title = {Lateral motion of a suspended spherical particle between two parallel moving walls}, booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2014}, month = {17{\textendash}20 Oct 2014}, pages = {SPP2014-PB-4}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
This study aims to determine the dynamics of a spherical particle that is suspended in a fluid that is confined between two parallel moving walls. A simulation was done using the molecular dynamics software LAMMPS. It was observed that the particle tends to move toward the wall nearer to it and that its equilibrium displacement is approximately proportional to its initial distance from the center. It was also observed that increasing the wall velocity increases the magnitude of this lateral displacement.
}, author = {Robert C Tacbad and Joshua Gregor A Dizon and Francis N. C. Paraan} } @inproceedings {baldo-spp-2014, title = {Magnetoconductance of a spin polarized electron along a curved one-dimensional wire}, booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2014}, month = {17{\textendash}20 Oct 2014}, pages = {SPP2014-1A-6}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
In this paper, we revisit our transport studies on the motion of a spin-polarized electron along a curved quantum wire under the presence of a uniform perpendicular magnetic field B and both the Rashba and Dresselhaus spin-orbit couplings (SOCs). Then from the previously derived output transmission coefficients, we numerically determine the magnetoconductance of the electron motion along the curved wire. Our results agree with our earlier reports that for large effective SOCs, the effects of B on spin switching is reduced. Moreover, we found that for a given energy\ E, the desired high MC ratio can be achieved by tuning B. Finally, with large R the MC reduces significantly due to adiabatic transport.
}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {delarosa-spp-2014, title = {Mode entanglement in squeezed coherent and displaced squeezed states}, booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2014}, month = {17{\textendash}20 Oct 2014}, pages = {SPP2014-5A-7}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
We study mode entanglement in four quantum states (coherent state, squeezed vacuum state, displaced squeezed state, squeezed coherent state), which are generated from a bosonic two-mode vacuum state by the action of displacement and squeezing operators. The mode entanglement entropy in these states is calculated and shown to depend only on the squeezing magnitude.
}, author = {Rafael S. dela Rosa and King Karl R Seroje and Francis N. C. Paraan} } @conference {354, title = {Simulation of Grover{\textquoteright}s algorithm with spatially-dependent coupling constant}, year = {2014}, month = {16{\textendash}25 Sep 2014}, pages = {19}, publisher = {Okinawa School in Physics: Coherent Quantum Dynamics}, address = {Okinawa Institute of Science and Technology, Japan}, abstract = {We simulate Grover{\textquoteright}s algorithm in an Ising spin chain quantum computer with spatially-dependent coupling constant. The simulation shows that the tendency of two distinct states to transition from the same initial state is reduced. The fidelity with the ideal result and the probability of finding the target state are also investigated.}, url = {https://groups.oist.jp/cqd/participants-0}, author = {Neris D Ilano and Cristine Villagonzalo and Ronald Banzon} } @inproceedings {tabernilla-spp-2014, title = {Speed-up and efficiency of parallelized Monte Carlo integration on homogeneous and heterogeneous clusters}, booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2014}, month = {17{\textendash}20 Oct 2014}, pages = {SPP2014-2C-6}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
We evaluate the performance of parallelized Monte Carlo integration algorithms on homogeneous and heterogeneous clusters of the Structure and Dynamics Laboratory. In this study, intrinsic pseudorandom number generators for Fortran and Python were used and parallelization achieved by MPI libraries. On an example using 10^9 samples, the parallelized Python code proved to be scalable on a cluster of up to 44 processors. The Fortran parallelized code performed less well on scalability but had a much shorter execution time. It was also observed that the overhead cost of parallelization saturates as the number of processors used increased.
}, author = {Ryan Carlos M Tabernilla and John Kevin R Sanchez and Francis N. C. Paraan} } @article {Baldo201493, title = {Spin-orbit coupled transport in a curved quantum wire}, journal = {Physica E}, volume = {63}, year = {2014}, note = {cited By 0}, pages = {93-98}, abstract = {
We study the interplay of both Rashba and Dresselhaus spin{\textendash}orbit couplings (SOCs) and a uniform perpendicular magnetic field B on the transport of a spin-polarized electron along a curved quantum wire. Eigenenergies and eigenfunctions of the system were analytically solved in the presence of both SOCs for a confinement radius R. From the transmission coefficients, the spin transport properties such as spin polarization, probability current density and spin conductance were computed numerically to determine their dependence on the SOCs, B and R. We find the condition for B that if it is beyond R1/3, no spin reversal will occur. Our results show that for a sufficiently large SOC strength, regardless of its inversion asymmetry origin, the effect of the external magnetic field is reduced. Finding the optimal effective SOC strength is essential in achieving suitable magneto-transport properties for possible spintronic device applications.
}, doi = {10.1016/j.physe.2014.05.013}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {323, title = {Work fluctuations in quantum quenches in the XY model}, booktitle = {Proceedings of the AQIS Conference 2014}, year = {2014}, month = {20{\textendash}24 Aug 2014}, pages = {193-194}, address = {Kyoto University, Japan}, abstract = {The emergent thermodynamics associated with quenching in the Heisenberg XY model is studied by calculating the fluctuations in the work done by an arbitrary quench. For certain post-quench parameters, non-analytic behavior in the work fluctuation as a function of pre-quench parameters can be used to locate the critical regions in the XY model phase diagram.}, url = {http://aqis-conf.org/2014/program/}, author = {Francis A Bayocboc Jr and Francis N. C. Paraan} } @inproceedings {ilano-spp-2014, title = {Working precision in a simulation of Grover{\textquoteright}s algorithm in an Ising spin system}, booktitle = {Proceedings of the 32nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2014}, month = {17{\textendash}20 Oct 2014}, pages = {SPP2014-5A-2}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
We consider the simulation of Grover{\textquoteright}s algorithm in an Ising nuclear spin chain computer with first- and second-nearest neighbor interaction. We calculate the fidelity, a measure of the accuracy of the state, as a function of π/2- and π-pulses and investigate the precision of the success probability of the target state. The fidelity is constrained by the set working precision of the computer system, hence we simulate the algorithm using different working precisions. A reduction of precision is also observed as you increase the number of iterations that restricts the size of the database to effectively simulate the algorithm. The amount of decrease is dependent on the decomposition of pulses.
}, author = {Neris D Ilano and Cristine Villagonzalo and Ronald S. Banzon} } @inproceedings {suico-spp-2013, title = {Characteristics of non-spanning clusters in a percolating two-dimensional square lattice}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-PB-10}, address = {University of San Carlos, Cebu City}, abstract = {
A study of interest in site percolation is to determine the characteristics of other clusters formed that do not span a given space. In this work we simulate on a square lattice of size L x L\ and show the behavior of the mean cluster size and its associated parameters near the percolation threshold. We find that at the percolation threshold the mean cluster size is proportional to L^1.656.
}, author = {Joachim Suico and Ronald S. Banzon and Cristine Villagonzalo} } @inproceedings {capili-spp-2013, title = {Determination of the percolation critical exponent as measure of dimension}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-4C-6}, address = {University of San Carlos, Cebu City}, abstract = {
The critical exponent\ β\ related to the percolation probability describes the dimensionality of a specific lattice topology. The\ accurate determination of\ β\ will aid in distinguishing different universality classes. This work describes the fine tuning of the\ Sigma method developed previously by the authors in obtaining\ β. The approach uses the log-log plot of the percolation\ probability versus the difference of the occupation probability and the percolation threshold. Considering a symmetric distribution of points about the midpoint of this plot yields the\ β\ with (1) the lowest standard deviation and (2) the\ appropriate asymptotic behavior for both one and two-dimensional lattices.
}, author = {Micielle N Capili and Ronald S. Banzon and Cristine Villagonzalo} } @inproceedings {ilano-spp-2013, title = {The effect of the Hadamard gate decomposition in the simulation of Grover{\textquoteright}s algorithm}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-5B-2}, address = {University of San Carlos, Cebu City}, abstract = {
Simulation of Grover{\textquoteright}s algorithm in an Ising nuclear spin chain computer with first- and second-nearest neighbor interaction is considered. The most frequently used quantum gate in the algorithm is the Hadamard gate. We investigate the effect of its decomposition into several rotation matrices and numerically calculate the fidelity and probability of success of finding the target state. Using an appropriate decomposition, we obtain a high fidelity for different numbers of iterations. The probability of finding the target state also increased and is much closer to the ideal result.
}, author = {Neris D Ilano and Cristine Villagonzalo and Ronald S. Banzon} } @inproceedings {puspus-spp-2013, title = {Entanglement entropy of impenetrable bosons in 1D: Effects of block length and boundaries}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-3B-7}, address = {University of San Carlos, Cebu City}, abstract = {
The effects of block length and boundary conditions on the entanglement entropy of two impenetrable bosons in separate spatial partitions of finite extent are studied in this paper. The von Neumann and R{\'e}nyi entropies decreased monotonically as the lengths of the block and environment become more and more unequal. Also, the system with periodic boundary conditions possesses a larger entanglement entropy than that with open boundaries.
}, author = {Xavier M Puspus and Francis N. C. Paraan} } @inproceedings {seroje-spp-2013, title = {Entanglement spectrum and entropy of two-mode squeezed vacuum states}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-3B-6}, address = {University of San Carlos, Cebu City}, abstract = {
Mode entanglement in a two-mode squeezed state is studied. The entanglement spectrum is derived and interpreted as Boltzmann coefficients of harmonic oscillator eigenstates at thermal equilibrium. The effective temperature is expressed in terms of squeezing parameters and is equal to zero when the state is unsqueezed and increases without bound as the state is infinitely squeezed. It is demonstrated that the reduced density operator can be identified as a canonical ensemble of single harmonic oscillator at some effective temperature Te. The R{\'e}nyi entanglement entropy is calculated and found to increase without bound as the squeezing parameter increases. The single-copy entanglement, which is a limiting value of the R{\'e}nyi entropy, is interpreted as a partition function.
}, author = {King Karl R Seroje and Francis N. C. Paraan} } @inproceedings {paraan-spp-2013, title = {Entanglement, statistical mechanics, and parallel computing}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-PS-04}, address = {University of San Carlos, Cebu City}, abstract = {
This talk has two parts. In the first, the concept of entanglement entropy in quantum information theory is presented in the context of principles of equilibrium statistical mechanics. The central object linking the two subjects is the reduced density operator. In the second part, a primer on two implementations of parallel computing in multisocket and multicore computers is given. Typical results of parallel programs using Message Passing Interface (MPI) and Open Multi-processing (OpenMP) are discussed to demonstrate the feasibility of parallel computing on desktop computers.
}, author = {Francis N. C. Paraan} } @inproceedings {tacbad-spp-2013, title = {Parallel speed-up and efficiency in single loop sums and matrix multiplication}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-PB-09}, address = {University of San Carlos, Cebu City}, abstract = {
This study aims to evaluate the performance of parallel implementations of single loop sums and matrix multiplication using the Message Passing Interface. Benchmark results were obtained from the available computing resources of the Structure and Dynamics Group (SanD). These implementations were run using 1 to 24 processors and their speed-up and efficiency were calculated. Nearly ideal speed up and efficiency was observed when tasks were distributed over physical cores of a single CPU.
}, author = {Robert C Tacbad and Francis N. C. Paraan} } @conference {356, title = {Signatures of Landau level crossings in a two-dimensional electron gas}, year = {2013}, month = {1{\textendash}5 Jul 2013}, pages = {MoP110}, publisher = {20th International Conference on Electronic Properties of Two-Dimensional Systems}, address = {Wroc{\l}aw University of Technology, Poland}, url = {http://www.ep2dsmss.org/}, author = {Rayda Gammag and Cristine Villagonzalo} } @inproceedings {baldo-spp-2013, title = {Spin switching on a quantum wire with spin orbit coupling in a uniform magnetic field}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-5B-4}, address = {University of San Carlos, Cebu City}, abstract = {
In this paper, the interplay of a uniform perpendicular magnetic field and the radius of curvature on the spin transport along a curved quantum wire with Rashba and Dresselhaus spin-orbit interactions is investigated. From the analytic calculations of the system{\textquoteright}s eigenenergies and eigenfunctions, transmission coefficients were numerically determined using transfer-matrix approach and were used to calculate the probability current densities and output polarization. Our results show that the spin orientation of the initially spin-polarized electron can be switched for smaller values of radius of curvature of the curved quantum wire. However, the range of spin switching is largely dependent on the threading magnetic field and on the strength of the spin-orbit interactions.
}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {cosme-spp-2013, title = {Thomas-Fermi approach on the particle density of a Tonks-Girardeau gas in harmonic confinement with multiple δ-perturbations}, booktitle = {Proceedings of the 31st Samahang Pisika ng Pilipinas Physics Congress}, year = {2013}, month = {23{\textendash}25 Oct 2013}, pages = {SPP2013-3B-2}, address = {University of San Carlos, Cebu City}, abstract = {
We investigate the Thomas-Fermi approach on the single particle density of a strongly interacting one dimensional bose gas under harmonic confinement with multiple localized δ barriers. We compare the resulting approximate of the density profile to exact density profiles that can be calculated for finite number of bosons. From the ground state energy, the corresponding chemical potential at T=0 is used to find the radius or extent of the density cloud.
}, author = {Jayson G Cosme and Francis N. C. Paraan and Jose Perico H Esguerra} } @article {Gammag201316, title = {Two-dimensional electron gas tilt-induced Landau level crossings}, journal = {Solid State Commun.}, volume = {156}, year = {2013}, note = {cited By 1}, pages = {16-20}, abstract = {
This work elucidates the novel behavior found in a two-dimensional electron gas (2DEG) under a tilted magnetic field in which the field{\textquoteright}s angle becomes the dominant factor in tuning the spin-splitting rather than the strength of the spin-orbit interaction. The 2DEG eigenvalues are derived with Rashba and Zeeman interactions for various tilt angles and they show crossing-free levels except at very high tilt. Moreover, concomitant with the crossings is the appearance of beats in the 2DEG density of states. The crossings from different levels occur consecutively at around 87{\textdegree}. Similar new observations in Shubnikov{\textendash}de Haas experimental measurements by Hatke et al. (2012) [6] attributed such phenomena to an in-plane-magnetic-field-induced increase in the effective mass. We show here that this behavior is inherent to a 2DEG where spin{\textendash}orbit interaction and the in-plane magnetic field contribution are taken into account.
}, doi = {10.1016/j.ssc.2012.12.006}, author = {Rayda Gammag and Cristine Villagonzalo} } @inproceedings {242, title = {The effect of RF distribution on the implementation of quantum CN gate in an Ising spin chain}, booktitle = {Proceedings of the 30th Samahang Pisika ng Pilipinas Physics Congress}, year = {2012}, month = {22{\textendash}24 Oct 2012}, pages = {SPP-2012-056}, address = {De La Salle Health Sciences Institute, Dasmari{\~n}as, Cavite}, abstract = {
We consider the dynamics of an Ising spin quantum computer with a radio frequency (RF) pulse distribution. The effect of the frequency spread decreases the resonant transition probability and increases thenear-resonant transition probability. Also, we apply the 2πk method to suppress the near-resonant transition. However, it has an unwanted effect on the probability of the resonant transition. It turns out that the desirable result can be obtained if we use the lowest possible value of k.
}, author = {Neris D Ilano and Cristine Villagonzalo and Ronald S. Banzon} } @article {Santos2012, title = {Entanglement spectra of q-deformed higher spin VBS states}, journal = {J. Phys. A: Math. Theor.}, volume = {45}, number = {17}, year = {2012}, note = {cited By 3}, pages = {175303}, abstract = {
We calculate the reduced density matrix of a block of integer spin-S{\textquoteright}s in a q-deformed valence-bond-solid (VBS) state. This matrix is diagonalized exactly for an infinitely long block in an infinitely long chain. We construct an effective Hamiltonian with the same spectrum as the logarithm of the density matrix. We also derive analytic expressions for the von Neumann and R{\'e}nyi entanglement entropies. For blocks of finite length, we calculate the eigenvalues of the reduced density matrix by perturbation theory and numerical diagonalization. These results enable us to describe the effects of finite-size corrections on the entanglement spectrum and entropy in this generalized VBS model.
}, doi = {10.1088/1751-8113/45/17/175303}, author = {Raul A Santos and Francis N. C. Paraan and Vladimir E Korepin and Andreas Kl{\"u}mper} } @article {Santos2012, title = {Entanglement spectra of the q-deformed Affleck-Kennedy-Lieb-Tasaki model and matrix product states}, journal = {Europhys. Lett.}, volume = {98}, number = {3}, year = {2012}, note = {cited By 4}, pages = {37005}, abstract = {
We exactly calculate the reduced density matrix of matrix product states (MPS). Our compact result enables one to perform analytic studies of entanglement in MPS. In particular, we consider the MPS ground states of two anisotropic spin chains. One is a q-deformed Affleck-Kennedy-Lieb-Tasaki (AKLT) model and the other is a general spin-1 quantum antiferromagnet with nearest-neighbor interactions. Our analysis shows how anisotropy affects entanglement on different continuous parameter manifolds. We also construct an effective boundary spin model that describes a block of spins in the ground state of the q-deformed AKLT Hamiltonian. The temperature of this effective model is given in terms of the deformation parameter q.
}, doi = {10.1209/0295-5075/98/37005}, author = {Raul A Santos and Francis N. C. Paraan and Vladimir E Korepin and Andreas Kl{\"u}mper} } @article {Gammag2012, title = {The interplay of Rashba spin-orbit interaction and Landau level broadening on a two-dimensional electron gas under a tilted magnetic field}, journal = {J. Phys. Conf. Ser.}, volume = {400}, number = {PART 4}, year = {2012}, note = {cited By 0}, pages = {042009}, abstract = {
A two-dimensional electron gas in a tilted magnetic field with Rashba spin-orbit interaction (RSOI) was studied. The RSOI is accredited to the asymmetry of the heterostructure where the two-dimensional electron gas is found. The effects of the disorder-attributed Landau level broadening and the RSOI on the spin splitting were identified by simulating the density of states which was assumed to take a Gaussian shape. Increased Landau level broadening obscures the spin splitting and increases the overlap between spin states resulting to stout Gaussian peaks. On the other hand, stronger RSOI amplifies the splitting and lessens the overlap between spin states of the Landau levels. The splitting, however, results to stouter peaks. The similarity in the RSOI and Landau level broadening effects can be explained by recognizing that the asymmetry of the heterostructure is in itself a form of structural disorder.
}, doi = {10.1088/1742-6596/400/4/042009}, author = {Rayda Gammag and Cristine Villagonzalo} } @article {BaldoIII2012, title = {Low-lying spin excitations due to next-nearest neighbour interactions in a ferromagnetic lattice with a body-centred cubic (bcc) crystal structure}, journal = {J. Phys. Conf. Ser.}, volume = {400}, number = {PART 3}, year = {2012}, note = {cited By 0}, pages = {032007}, abstract = {
Spin excitations due to the next-nearest-neighbour interactions are investigated for a ferromagnetic lattice with a body-centred cubic (bcc) crystal structure. Using the three-dimensional Heisenberg spin model in a uniform external magnetic field, both the nearest-neighbour (NN) and next-nearest-neighbour (NNN) exchange interactions are considered. The spin wave energies at low temperatures are calculated for which the system is close to its ground state. From the dispersion plots, the additional exchange interactions by the NNN cause an increase in the spin excitation energies. Furthermore, there is a critical NNN/NN exchange ratio for which the effect of the NNN interactions becomes evident as characterized by the presence of two maximum energy peaks in the energy spectra.
}, doi = {10.1088/1742-6596/400/3/032007}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {245, title = {Percolation critical exponent of a constrained lattice}, booktitle = {Proceedings of the 30th Samahang Pisika ng Pilipinas Physics Congress}, year = {2012}, month = {22{\textendash}24 Oct 2012}, pages = {SPP-2012-004}, address = {De La Salle Health Sciences Institute, Dasmari{\~n}as, Cavite}, abstract = {
We implement the Average Occupation Probability method to treat site percolation on a square lattice with banned sites. It was found that the introduction of banned sites increases the value of the percolation probability while reducing the value of the critical exponent\ β. The deviation of\ β\ in site percolation of a constrained lattice from that of a regular system suggests that these\ lattice\ topologies belong to two different universality classes.
}, author = {Micielle N Capili and Cristine Villagonzalo and Ronald S. Banzon} } @article {Gammag2012, title = {Persistent spin splitting of a two-dimensional electron gas in tilted magnetic fields}, journal = {Eur. Phys. J. B}, volume = {85}, number = {1}, year = {2012}, note = {cited By 1}, pages = {22}, abstract = {
By varying the orientation of the applied magnetic field with respect to the normal of a two-dimensional electron gas, the chemical potential and the specific heat reveal persistent spin splitting in all field ranges. The corresponding shape of the thermodynamic quantities distinguishes whether the Rashba spin-orbit interaction (RSOI), the Zeeman term or both dominate the splitting. The interplay of the tilting of the magnetic field and RSOI resulted to an amplified splitting even in weak fields. The effects of changing the RSOI strength and the Landau level broadening are also investigated.
}, doi = {10.1140/epjb/e2011-20615-x}, author = {Rayda Gammag and Cristine Villagonzalo} } @article {Santos2012, title = {Quantum phase transition in a multicomponent anyonic Lieb-Liniger model}, journal = {Phys. Rev. B}, volume = {86}, number = {4}, year = {2012}, note = {cited By 2}, pages = {045123}, abstract = {
We study a one-dimensional multicomponent anyon model that reduces to a multicomponent Lieb-Liniger gas of impenetrable bosons (Tonks-Girardeau gas) for vanishing statistics parameter. At fixed component densities, the coordinate Bethe ansatz gives a family of quantum phase transitions at special values of the statistics parameter. We show that the ground-state energy changes extensively between different phases. Special regimes are studied and a general classification for the transition points is given. An interpretation in terms of statistics of composite particles is proposed.
}, doi = {10.1103/PhysRevB.86.045123}, author = {Raul A Santos and Francis N. C. Paraan and Vladimir E Korepin} } @article {Gammag2012757, title = {Quenching of the DOS beats in a two-dimensional electron gas in tilted magnetic fields}, journal = {Solid State Commun.}, volume = {152}, number = {9}, year = {2012}, note = {cited By 2}, pages = {757-761}, abstract = {
A two-dimensional electron gas exposed to a tilted magnetic field is considered with the Rashba spin{\textendash}orbit interaction and the Zeeman effect. An exact solution for the eigenvalues was obtained assuming that two opposite spin states of adjacent Landau levels have equal probability. No crossings between adjacent eigenenergies were observed, for the tilt angles studied here (θ<=80{\textdegree}), unlike in the perpendicular-magnetic-field case. The absence of crossings leads to quenched beating structures in the oscillations of the density of states (DOS). Persistent spin-splittings were observed at the weak magnetic field region. The splittings, however, can be effectively screened by an increased Landau level broadening. The results shed light on how spins can be controlled through the Rashba interaction strength, the disorder-related broadening and the magnetic field tilt angle.
}, doi = {10.1016/j.ssc.2012.01.047}, author = {Rayda Gammag and Cristine Villagonzalo} } @inproceedings {244, title = {Rashba and Dresselhaus spin-orbit interactions in a curvilinear motion of a spin-polarized electron}, booktitle = {Proceedings of the 30th Samahang Pisika ng Pilipinas Physics Congress}, year = {2012}, month = {22{\textendash}24 Oct 2012}, pages = {SPP-2012-054}, address = {De La Salle Health Sciences Institute, Dasmari{\~n}as, Cavite}, abstract = {
To see the effects of both Rashba and Dresselhaus spin-orbit interactions on a spin-polarized electron along a curved path, we obtain the system{\textquoteright}s exact energy spectrum taking into account the Zeeman effect. This approximates the motion of an electron in a one-dimensional wire. Our results show that the lifted degeneracy between spins of opposite polarization does not only depend on both Rashba and Dresselhaus coupling constants, but also on the radius of curvature.
}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @article {Pi{\~n}ol2011101, title = {Catastrophic senescence and semelparity in the Penna aging model}, journal = { Theory Biosci.}, volume = {130}, number = {2}, year = {2011}, note = {cited By 2}, pages = {101-106}, abstract = {
The catastrophic senescence of the Pacific salmon is among the initial tests used to validate the Penna aging model. Based on the mutation accumulation theory, the sudden decrease in fitness following reproduction may be solely attributed to the semelparity of the species. In this work, we report other consequences of mutation accumulation. Contrary to earlier findings, such dramatic manifestation of aging depends not only on the choice of breeding strategy but also on the value of the reproduction age, R, and the mutation threshold, T. Senescence is catastrophic when T <= R. As the organism{\textquoteright}s tolerance for harmful genetic mutations increases, the aging process becomes more gradual. We observe senescence that is threshold dependent whenever T \> R. That is, the sudden drop in survival rate occurs at age equal to the mutation threshold value.
}, doi = {10.1007/s12064-010-0115-7}, author = {Chrysline Margus N Pi{\~n}ol and Ronald Banzon} } @inproceedings {248, title = {Determination of the critical exponent β in site percolation using average occupation probability on a square lattice}, booktitle = {Proceedings of the 29th Samahang Pisika ng Pilipinas National Physics Congress}, year = {2011}, month = {24{\textendash}26 Oct 2011}, pages = {SPP2011-5A-3}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
Using the Average Occupation Probability in site percolation, the critical exponent\ β\ for a lattice (L {\texttimes} L) is determined. The results for different lattice\ sizes show that as the lattice becomes larger, the calculated\ β\ agrees better with that obtained from 2D scaling theory. There appears a common\ range of p-pc which can be used for any L to compute for\ β. We estimate that a minimum lattice size of 200 {\texttimes} 200 is necessary for the\ procedure to yield an acceptable value of the critical exponent.
}, url = {https://paperview.spp-online.org/proceedings/article/view/3139}, author = {Micielle N Capili and Cristine Villagonzalo and Ronald S. Banzon} } @article {Paraan2011, title = {Entanglement in bipartite pure states of an interacting boson gas obtained by local projective measurements}, journal = {Phys. Rev. A}, volume = {84}, number = {3}, year = {2011}, note = {cited By 1}, pages = {032330}, abstract = {

We quantify the extractable entanglement of excited states of a Lieb-Liniger gas that are obtained from coarse-grained measurements on the ground state in which the boson number in one of two complementary contiguous partitions of the gas is determined. Numerically exact results obtained from the coordinate Bethe ansatz show that the von Neumann entropy of the resulting bipartite pure state increases monotonically with the strength of repulsive interactions and saturates to the impenetrable-boson limiting value. We also present evidence indicating that the largest amount of entanglement can be extracted from the most probable projected state having half the number of bosons in a given partition. Our study points to a fundamental difference between the nature of the entanglement in free-bosonic and free-fermionic systems, with the entanglement in the former being zero after projection, while that in the latter (corresponding to the impenetrable-boson limit) being nonzero.

}, doi = {10.1103/PhysRevA.84.032330}, author = {Francis N. C. Paraan and Javier Molina-Vilaplana and Vladimir E Korepin and Sougato Bose} } @article {Villagonzalo201143, title = {The intrinsic features of the specific heat at half-filled Landau levels of two-dimensional electron systems}, journal = {J. Low Temp. Phys.}, volume = {163}, number = {1-2}, year = {2011}, note = {cited By 2}, pages = {43-52}, abstract = {
The specific heat capacity of a two-dimensional electron gas is derived for two types of the density of states, namely, the Dirac delta function spectrum and that based on a Gaussian function. For the first time, a closed form expression of the specific heat for each case is obtained at half-filling. When the chemical potential is temperature-independent, the temperature is calculated at which the specific heat is a maximum. Here the effects of the broadening of the Landau levels are distinguished from those of the different filling factors. In general, the results derived herein hold for any thermodynamic system having similar resonant states.
}, doi = {10.1007/s10909-010-0259-3}, author = {Cristine Villagonzalo and Rayda Gammag} } @inproceedings {ilano-spp-2011, title = {Optimizing the damped quantum search algorithm}, booktitle = {Proceedings of the 29th Samahang Pisika ng Pilipinas National Physics Congress}, year = {2011}, month = {24{\textendash}26 Oct 2011}, pages = {SPP2011-4A-4}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
An optimization of the damped quantum search is introduced by calculating the damping parameter that gives the minimum probability of failure per iteration. The resulting damping parameter is compared with the critical damping. The result shows that the optimized damping is generally not equal to the critical damping if the degeneracy of the target state is not comparable to the size of the database. The probability of failure for the optimized damping and critical damping does not differ significantly for the first two iterations. This difference is relatively large for the third iteration. This suggests that for greater number of iterations, the critically damped search is not optimized.
}, url = {https://paperview.spp-online.org/proceedings/article/view/3135}, author = {Neris D Ilano and Ronald S. Banzon and Cristine Villagonzalo} } @inproceedings {249, title = {Persistence in the zero temperature dynamics of the 1D Ising model with long range interactions}, booktitle = {Proceedings of the 29th Samahang Pisika ng Pilipinas National Physics Congress}, year = {2011}, month = {24{\textendash}26 Oct 2011}, pages = {SPP2011-PB-33}, address = {University of the Philippines Diliman, Quezon City}, abstract = {
We study the zero-temperature dynamics of the 1D Ising Model with long range interactions. In particular, we focus on the persistence behavior as the strength of the long range interaction is varied. Persistence pertains to those spins that did not flip after some time. We observe that whatever the strength of the long range interaction, the system exhibits blocking where some spins do not flip at all. The system size is also varied to see its effect on these properties.
}, url = {https://paperview.spp-online.org/proceedings/article/view/3240}, author = {Hilton Lazo and Ronald Banzon and Cristine Villagonzalo} } @article {Pi{\~n}ol20111295, title = {Stability in a population model without random deaths by the Verhulst factor}, journal = {Physica A}, volume = {390}, number = {7}, year = {2011}, note = {cited By 1}, pages = {1295-1299}, abstract = {
A large amount of population models use the concept of a carrying capacity. Simulated populations are bounded by invoking finite resources through a survival probability, commonly referred to as the Verhulst factor. The fact, however, that resources are not easily accounted for in actual biological systems makes the carrying capacity parameter ill-defined. Henceforth, we deem it essential to consider cases for which the parameter is unnecessary. This work demonstrates the possibility of Verhulst-free steady states using the Penna aging model, with one semelparous birth per adult. Stable populations are obtained by setting a mutation threshold that is higher than the reproduction age.
}, doi = {10.1016/j.physa.2010.11.046}, author = {Chrysline Margus N Pi{\~n}ol and Ronald S. Banzon} } @inproceedings {antoniospp2010, title = {Characterization of an Ising-Like SI model}, booktitle = {Proceedings of the 28th Samahang Pisika ng Pilipinas Physics Congress}, year = {2010}, month = {25{\textendash}27 Oct 2010}, pages = {SPP-2010-003}, address = {Meralco Management and Leadership Development Center, Antipolo City}, abstract = {
An Ising-like system was used to model a computer network through which malware is spreading. The rate of spread of infection was estimated by fitting the infection curves with a standard logistic model and an exponential model. Graphical analysis shows that the exponential decay model fit the infection curves better than the logisitic model. Trends in the residuals suggest that current mathematical models for epidemics are not consistent with the system.
}, author = {Kristine Eia S Antonio and Ronald S. Banzon} } @conference {358, title = {Long range disorder effects on the heat capacity of two-dimensional electron systems}, year = {2010}, month = {12{\textendash}15 Dec 2010}, pages = {66-67}, publisher = {9th Asia-Pacific Workshop on Materials Physics}, address = {Hanoi University of Science, Vietnam}, abstract = {Broadening of Landau levels of two dimensional electron systems at low temperature and at high perpendicular magnetic fields causes perceptible variations in their interlevel and intralevel excitations as seen in their heat capacity. At a characteristic temperature, the interlevel excitations become negligible and the effect of a small broadening on the energy spectrum vanishes. In this work, a long-range disorder is considered. This can be modeled for the two-dimensional electron gas via a Lorentzian density of states or a Gaussian density of states whose broadening is much larger than kT. The temperature dependence of the heat capacity is derived at half-filled Landau levels or when the chemical potential is a constant. The heat capacity behavior of a system with a long-range disorder is compared to the case of impurity-free quantum Hall systems.}, url = {http://www.iop.vast.ac.vn/theor/conferences/apwmp/files/Detailed\%20Program.pdf}, author = {Cristine Villagonzalo and Rayda P Gammag} } @conference {357, title = {Penna model estimate of improved medical care in the Philippines}, year = {2010}, month = {14{\textendash}16 Jun 2010}, pages = {59}, publisher = {10th Science Council of Asia Conference}, address = {Pasay City}, abstract = {The average life expectancy at birth is one indicator of the overall health of a country. In a Penna model that accounts for enhancements in medical services and welfare, the effect of heritable diseases is diminished. Individuals may live longer with probability equal to the relative increase in health care. Choosing the 1950 data for the Philippine population as baseline, the 44\% rise in average life span of Filipinos from then to 1995 may be attributed to a 20\% improvement in medical care. The 2010 life expectancy estimate follows from a 6\% increase in the quality of medical assistance during the last 15 years.}, url = {http://www.scj.go.jp/en/sca/activities/conferences/conf_10.html}, author = {Chrysline Margus N Pi{\~n}ol and Ronald S. Banzon} } @inproceedings {258, title = {Penna model estimate of medical care improvement}, booktitle = {Proceedings of the 28th Samahang Pisika ng Pilipinas Physics Congress}, year = {2010}, month = {25{\textendash}27 Oct 2010}, pages = {SPP-2010-001}, address = {Meralco Management and Leadership Development Center, Antipolo City}, abstract = {
Quantitative estimates for the quality of care are obtained from a Penna model that incorporates medical care. Enhancements in health services and welfare increase the average lifespan by decreasing the effect of heritable diseases. Feasibility of the approach was demonstrated by fitting simulation results with the Philippine life expectancy data. We find that the relative increase in lifespan is proportional to the improvement in care. The Penna model estimates of life expectancy compare well with the UN projections for the Philippine population.
}, author = {Chrysline Margus Pi{\~n}ol and Ronald S. Banzon} } @article {Paraan2010, title = {Perturbative correction to the ground-state properties of one-dimensional strongly interacting bosons in a harmonic trap}, journal = {Phys. Rev. A}, volume = {82}, number = {6}, year = {2010}, note = {cited By 2}, pages = {065603}, abstract = {
We calculate the first-order perturbation correction to the ground-state energy and chemical potential of a harmonically trapped boson gas with contact interactions about the infinite repulsion Tonks-Girardeau limit. With c denoting the interaction strength, we find that, for a large number of particles N, the 1/c correction to the ground-state energy increases as N^5/2, in contrast to the unperturbed Tonks-Girardeau value that is proportional to N^2. We describe a thermodynamic scaling limit for the trapping frequency that yields an extensive ground-state energy and reproduces the zero temperature thermodynamics obtained by a local-density approximation.
}, doi = {10.1103/PhysRevA.82.065603}, author = {Francis N. C. Paraan and Vladimir E Korepin} } @inproceedings {baldospp2010, title = {Spin waves in a simple ferromagnetic cubic lattice using the Heisenberg model with nearest and next-nearest neighbor interactions}, booktitle = {Proceedings of the 28th Samahang Pisika ng Pilipinas Physics Congress}, year = {2010}, month = {25{\textendash}27 Oct 2010}, pages = {SPP-2010-006}, address = {Meralco Management and Leadership Development Center, Antipolo City}, abstract = {
We study the combined effect of the nearest and the next-nearest neighbor interactions on the spin wave dispersion of an isotropic cubic ferromagnet in a uniform magnetic field using the Heisenberg model. Near the groundstate, the components of the spin angular momentum perpendicular to the applied field are negligible as compared to the parallel spin component. Hence, the dispersion relation and the ground state energy estimate of the system are obtained by considering the spin fluctuations along the plane normal to the magnetic field. The results herein are compared to the case where only the effect of the nearest neighbors are present.
}, author = {Carlos F Baldo III and Cristine Villagonzalo} } @inproceedings {257, title = {Uncertainty relation of the momentum components of a two-dimensional electron system under a tilted magnetic field}, booktitle = {Proceedings of the 28th Samahang Pisika ng Pilipinas Physics Congress}, year = {2010}, month = {25{\textendash}27 Oct 2010}, pages = {SPP-2010-005}, address = {Meralco Management and Leadership Development Center, Antipolo City}, abstract = {
A two-dimensional electron gas along the xy-plane is considered. When an applied perpendicular magnetic field, directed along the z-axis, is turned on, the electrons move in cyclotron orbits and the components of the momentum along the x- and y-axes do not commute. This work shows that if the applied magnetic field is tilted at an angle\ θ\ with respect to the z-axis, the uncertainty in simultaneous measurements of the momentum components becomes dependent on\ θ.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @article {gammag2009a, title = {Crossover of the specific heat from the quantum Hall to the classical regime}, journal = {AIP Conf. Proc.}, volume = {1119}, year = {2009}, pages = {213}, abstract = {

The specific heat, CV, of a two-dimensional electron system in the quantum Hall effect (QHE) regime was calculated numerically. A peak was observed at temperature Tp uniform to all filling factors. This Tp signified the shift of dominance from the extended states to the localized states. After the peak decays CV rose again, this time reflecting the destruction of the QHE and the emergence of the classical counterpart. The classical Hall was characterized by a T-invariant chemical potential.

}, doi = {http://dx.doi.org/10.1063/1.3137811}, author = {Rayda Gammag and Cristine Villagonzalo} } @inproceedings {ilano-spp-2009, title = {Damped quantum search in an Ising spin system}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-006}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
We seek on 8 and a 12 spins Ising systems at least one of their eigenstates of a certain eigenvalue by applying the damped quantum search. In particular, without the knowledge of the number of degeneracy, it requires 150 queries to find at least one of the characteristic states having an eigenvalue of -11ε in a database of 4096 items with a probability of 99.1\%. The average number of queries are compared with that of the undamped quantum search. It is found that for a small number of target states, the damped quantum search still preserves the quantum results, while for a large number of target states the classical limit is approached. Moreover, the damped quantum search is shown to increase monotonically as the number of iteration is increased.
}, author = {Neris D Ilano and Ronald S. Banzon and Cristine Villagonzalo} } @article {jacosalem2009a, title = {Numerical investigations of symmetric embedded quantum well systems using the shooting method and transfer matrix technique}, journal = {AIP Conf. Proc.}, volume = {1119}, year = {2009}, pages = {219}, abstract = {
Embedded quantum well systems are constructed via a superposition of modified P{\"o}schl-Teller (MPT) potentials. To illustrate the advantages and/or disadvantages of each system, a comparison is made on their energy spectra and scattering properties. The bound states of each system are obtained using the numerical shooting method. The accuracy of this method depends on the step length δz, which can be completely controlled, allowing an improved comparison with analytical solutions to be achieved. A systematic approach of finding the eigenenergies En (n = 0, 1, 2, 3, {\textellipsis}) is also developed in this work. The approach utilizes the established bisection method{\textemdash}a root-finding algorithm that repeatedly divides an interval in half then selects the subinterval in which a root exists. Here selective bisection is implemented for computational efficiency. This entire procedure in finding the solutions of the Schr{\"o}dinger equation is tested for a single MPT well where the solution is analytically known. The result shows a perfect agreement between the numerical and the analytical method. The transfer matrix approach is used to obtain the transmission probability of a particle passing through the embedded quantum well systems. This technique also shows a perfect agreement with the analytical solution.
}, doi = {http://dx.doi.org/10.1063/1.3137825}, author = {Naomi Jane Jacosalem and Cristine Villagonzalo} } @inproceedings {pinol-spp-2009, title = {Obtaining finite populations in a Verhulst-free 8-bit Penna model with periodic change in reproduction}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-033}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
Periodic changes in reproduction age slow down population growth or decay. The minimum reproductive age in an 8-bit, Verhulst-free Penna model varied repeatedly between two values. It is an invariable characteristic of an individual which is set at birth. A steady state is found when the period for the smaller reproductive age is slightly longer.
}, author = {Chrysline Margus Pi{\~n}ol and Ronald S. Banzon} } @inproceedings {johnson-spp-2009, title = {One dimensional migration of DNA in the presence of point particle traps}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-071}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
This paper studies the one-dimensional motion of a DNA molecule through a microchannel with a series of point particle electric traps. The three particle molecule model uses three beads connected via harmonic springs in the presence of a Weeks Chandler-Andersen repulsive potential and a Brownian force. Using the stochastic fourth order Runge-Kutta method, the trajectory of the center of mass is observed as the field strengths were varied. System parameters are identified that can impede the flow of a DNA molecule.
}, author = {Sarah Johnson and Cristine Villagonzalo} } @article {Paraan2009, title = {Quantum quenches in the Dicke model: Statistics of the work done and of other observables}, journal = {Phys. Rev. E}, volume = {80}, number = {6}, year = {2009}, note = {cited By 14}, pages = {061130}, abstract = {
We study the statistics of the work done in a zero temperature quench of the coupling constant in the Dicke model describing the interaction between an ensemble of two level systems and a single bosonic mode. When either the final or the initial coupling constants approach the critical coupling λc that separates the normal and superradiant phases of the system, the probability distribution of the work done displays singular behavior. The average work tends to diverge as the initial coupling parameter is brought closer to the critical value λc. In contrast, for quenches ending close to criticality, the distribution of work has finite moments but displays a sequence of edge singularities. This contrasting behavior is related to the difference between the processes of compression and expansion of a particle subject to a sudden change in its confining potential. We confirm this by studying in detail the time-dependent statistics of other observables, such as the quadratures of the photons and the total occupation of the bosonic modes.
}, doi = {10.1103/PhysRevE.80.061130}, author = {Francis N. C. Paraan and Alessandro Silva} } @inproceedings {antonio-spp-2009, title = {Selecting a practical successive over relaxation parameter for a particle-in-cell method}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-156}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
The rate of convergence of the Successive Over-Relaxation (SOR) method depends on the choice of SOR Parameter,\ ω. It is shown\ that the SOR method as a Poisson Solver in the Particle-in-Cell (PIC), has a practical SOR parameter,\ ωp, that is independent\ of the number of particles contained by the system. A method that speeds up the selection of this\ ωp\ is proposed.\ For a 16x16 Plasma PIC system, using 7 test points and an increment of s = 0.03215, the\ ωp\ selected by the method is\ 1.71 which is equal to the\ ωp\ determined from a parameter scan.
}, author = {Kristine Eia S Antonio and Ronald S. Banzon} } @inproceedings {gammag-spp-2009, title = {Sensitivity of the specific heat to the electronic density of states}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-062}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
The effect of an anomalous shape of the electronic density of states near the Fermi energy on the specific heat for bulk solids is investigated in this work. The density of states was simulated using a superposition of the usual square-root-energy-dependent function, and an additional Gaussian function centered in the region about the Fermi energy. The results show an enhanced specific heat when the anomalous density of states{\textquoteright} peak is located after but near the Fermi energy. If this peak is narrow, the specific heat displays an extra maximum with temperature. A large specific heat is suitable for applications wherein it is preferred to keep a system at constant temperature despite a large thermal energy exchange with its environment.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @inproceedings {lazo-spp-2009, title = {Site percolation of a fixed lattice size with growing regions of disallowed occupancy}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-036}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
We study site percolation in a rectangular lattice with increasing size of two clumped groups of banned sites. The percolation threshold was found to increase as the size of the banned sites is increased. The results were compared to the previously studied lattice with a system with a single group of clumped banned sites with the same number of available sites for occupation. It was observed that the percolation threshold for the dual case is greater than that of the single case. However, the thresholds follow the same trend as the number of available sites is increased.
}, author = {Hilton Lazo and Cristine Villagonzalo and Ronald S. Banzon} } @inproceedings {panganiban-spp-2009, title = {Thresholds of percolating systems with two symmetric forbidden zones having a constant separation}, booktitle = {Proceedings of the 27th Samahang Pisika ng Pilipinas Physics Congress}, year = {2009}, month = {28{\textendash}30 Oct 2009}, pages = {SPP-2009-034}, address = {Development Academy of the Philippines Convention Center, Tagaytay City}, abstract = {
In this paper, we investigate the percolation thresholds for a two-dimensional system with two square banned sites, its topological equivalence with another system with a single square banned site, and the scaling property between their thresholds. An eight-corner check algorithm was implemented to evaluate the percolation of this dual banned sites system. We found that percolation threshold for the dual case follows the same trend as the single case, where the threshold increases as the banned site dimension (X) is increased. Our results suggest that the thresholds for the single and dual case are related by some finite scaling laws.
}, author = {Earl Angelo Panganiban and Cristine Villagonzalo and Ronald S. Banzon} } @article {villagonzalo2009a, title = {Women in physics in the Philippines: Quantized yet taking steps toward a mature science culture}, journal = {AIP Conf. Proc.}, volume = {1119}, year = {2009}, pages = {155-156}, abstract = {
Scientific culture in the Philippines is young and physics is no exception. There are only four physics PhD-granting universities with research laboratories. More than 10 universities offer a bachelor{\textquoteright}s degree or master{\textquoteright}s degree in Physics. Like the world trend, these physics institutions are male dominated. However, four of the leading universities already have female PhD faculty members in physics occupying positions of an assistant professor or better. On a positive note, female physicists are no longer limited to work in the national capital region but have carved out their careers in other parts of the country. Also, female physicists have spread into other non-physics-degree-granting universities or found work in the industrial sector. The number of female graduates in physics in the undergraduate and graduate level have slowly but steadily increased since 2002. With the observed increase in number, a working group for women in physics in the Philippines was created this year. In order to provide recommendations to regulators and policy makers, the group{\textquoteright}s first step is to monitor the number of female students and physicists, their study and work environments, and the scholarships and opportunities for development that are available to them.
}, doi = {http://dx.doi.org/10.1063/1.3137751}, author = {Cristine Villagonzalo and Jinky Bornales and Jelly Grace Betoya-Nonesa} } @inproceedings {gammag-spp-2008, title = {The 2DES chemical potential: Revealing the link from the classical to the quantum Hall regime}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-026}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
A two-dimensional electron system under a magnetic field was studied numerically particularly, the temperature dependence of its chemical potential. For all fillings ν the chemical potential μ saturated to a common value at high temperature T - the classical Hall region. Approaching low T, the quantum Hall regime, μ followed varying paths depending on ν. For the complete fillings, μ showed a knee temperature Tν pointing to the juncture between the two regimes. This crossover, characterized by Tν being constant, indicates the balance between the localization and delocalization effects of the magnetic field and temperature, respectively.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @article {Paraan2008, title = {Brownian motion of a charged particle driven internally by correlated noise}, journal = {Phys. Rev. E}, volume = {77}, number = {2}, year = {2008}, note = {cited By 12}, pages = {022101}, abstract = {
We give an exact solution to the generalized Langevin equation of motion of a charged Brownian particle in a uniform magnetic field that is driven internally by an exponentially correlated stochastic force. A strong dissipation regime is described in which the ensemble-averaged fluctuations of the velocity exhibit transient oscillations that arise from memory effects. Also, we calculate generalized diffusion coefficients describing the transport of these particles and briefly discuss how they are affected by the magnetic field strength and correlation time. Our asymptotic results are extended to the general case of internal driving by correlated Gaussian stochastic forces with finite autocorrelation times.
}, doi = {10.1103/PhysRevE.77.022101}, author = {Francis N. C. Paraan and Mikhail P Solon and Jose Perico Esguerra} } @article {Gammag2008487, title = {The interplay of Landau level broadening and temperature on two-dimensional electron systems}, journal = {Solid State Commun.}, volume = {146}, number = {11-12}, year = {2008}, note = {cited By 5}, pages = {487-490}, abstract = {
This work investigates the influence of low temperature and broadened Landau levels on the thermodynamic properties of two-dimensional electron systems. The interplay between these two physical parameters on the magnetic field dependence of the chemical potential, the specific heat and the magnetization is calculated. In the absence of a complete theory that explains the Landau level broadening, experimental and theoretical studies in literature perform different model calculations of this parameter. Here it is presented that different broadening parameters of Gaussian-shaped Landau levels cause width variations in their contributions to interlevel and intralevel excitations. Below a characteristic temperature, the interlevel excitations become negligible. Likewise, at this temperature range, the effect of the Landau level broadening vanishes.
}, doi = {10.1016/j.ssc.2008.03.042}, author = {Rayda P Gammag and Cristine Villagonzalo} } @inproceedings {jacosalem-spp-2008, title = {Realignment of energy spectra of modified P{\"o}schl-Teller potentials in a composite quantum well-in-a-well system}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-021}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
Quantum well-in-a-well (QWW) systems are constructed via a superposition of modified Poschl-Teller potential wells. The systems are constructed such that the bound states of the component side wells correspond exactly to the excited states of the constituent center well. The energy spectra of these systems are obtained using the shooting method. The contribution of each component well on the total number of bound states of the constructed composite system is presented. Results show that the middle component well is the dominant contributor to the total number of bound states of the QWW system. All contributions are accounted for, however, they are shifted relative to the initial energy level.
}, author = {Naomi Jane Jacosalem and Cristine Villagonzalo} } @inproceedings {uy-spp-2008, title = {Regions of constant earth magnetic fields}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-175}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
Approximating the magnetic field surrounding the Earth to be due to that of a dipole, we determine effective regions of constant field. Each region was identified utilizing as basis the outline of a circular trajectory for a charged particle that travels in the equatorial plane. The trajectories were obtained by indicating the center and radius of the circles. It was found that as the distance of the center of the circular trajectory from the Earth is increased, the radius of the trajectory increases. Increasing the particle{\textquoteright}s initial velocity also increased the radius of the trajectory.
}, author = {Toni Lei Uy and Ronald S. Banzon} } @inproceedings {pi{\~n}ol-spp-2008, title = {Reproduction age and survival of a Verhulst-free 8-bit Penna population}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-071}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
A Verhulst-free Penna model is shown to be equivalent to a Malthusian model. The population is driven to exponentially increase or decrease with time depending on the value of its minimum reproductive age. This demonstration justifies its identification as a critical parameter. Unlike the Malthusian model however, we are able to obtain a relatively persistent population by imposing a distribution for the critical minimum reproductive age values.
}, author = {Chrysline Margus Pi{\~n}ol and Ronald S. Banzon} } @inproceedings {johnson-spp-2008, title = {Simulation of DNA mobility in one-dimension using the bead-spring model}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-138}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
This paper studies the one-dimensional motion of a DNA molecule through a microchannel with a single electric trap. The three particle molecule model uses three beads connected via harmonic springs in the presence of a Weeks-Chandler-Andersen repulsive potential and a Brownian force. Using the stochastic fourth order Runge-Kutta method, the spring constant is sought that allows motion through the microchannel without overlap between the three beads.
}, author = {Sarah Johnson and Cristine Villagonzalo} } @inproceedings {amarra-spp-2008, title = {Simulation of Grover{\textquoteright}s algorithm on a one-dimensional two-level Ising spin system}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-004}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
We present an application of Grover{\textquoteright}s search algorithm for quantum computers to the one-dimensional Ising model. In particular, a linear, open ferromagnetic system of four spins is considered, and the algorithm is used to find the six states having energy -ε. By using the Hamiltonian operator, the action of a phase-flipping oracle is defined. An 84\% probability of success is obtained after one iteration.
}, author = {Anthony Amarra and Cristine Villagonzalo and Ronald S. Banzon} } @inproceedings {hernal-spp-2008, title = {Spanning a space in a quasi-one dimensional lattice vs. two-dimensional lattice with square banned sites}, booktitle = {Proceedings of the 26th Samahang Pisika ng Pilipinas Physics Congress}, year = {2008}, month = {22{\textendash}24 Oct 2008}, pages = {SPP-2008-163}, address = {University of the Phlippines Baguio, Baguio City}, abstract = {
Percolation thresholds in quasi- one and two dimensional systems were compared. In the former, one-way spanning is employed with a spanning cluster defined as an array that extends horizontally from one end of the lattice to the other. A four-corner checking procedure is introduced in this study to measure the percolation threshold in the corresponding two-dimensional systems with square banned sites (2DSBS). The results indicate that the threshold values from the two methods converge suggesting that the quasi-1D system and the 2DSBS are equivalent topologically.
}, author = {Mary Joyce Hernal and Cristine Villagonzalo and Ronald S. Banzon} } @inproceedings {castro-spp-2007, title = {Analysis of symmetric solutions to the Ginzburg-Landau equations for superconducting films}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-177}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
Superconductivity in films in a tangential external magnetic field is simulated using a one-dimensional Ginzburg-Landau (GL) model. A symmetric solution to the GL equations is sought using a central difference approximation. This work will illustrate the behavior of superconducting electrons across thick and thin films for various magnetic field strengths. The Meissner effect for type-1 and type II superconductors is verified.
}, author = {Criswelynn D Castro and Cristine Villagonzalo} } @inproceedings {cortez-spp-2007, title = {Analysis of transient heat conduction on aluminum and iron contacts}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-115}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
In this paper, transient temperature profiles for material configurations involving Al-Fe layers in contact with continuous and single pulse heat sources are obtained. A stable and convergent solution is achieved by imposing a suitable Courant-Friedrichs-Lewy (CFL) condition. The magnitude of the effective thermal conductivity of composite materials as compared to their homogeneous counterparts is demonstrated to rise as the number of contacts increases.
}, author = {April D Cortez and Cristine Villagonzalo} } @inproceedings {capili-spp-2007, title = {Calculation of the average occupation probability for spanning cluster formation in site percolation}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-192}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
The average occupation probability for spanning cluster formation in square lattice using site percolation was calculated. Starting with an empty lattice, sites were generated using a pseudo-random number generator. A cluster labeling procedure was implemented for the detection of a spanning cluster. Our results show that the average occupation probability decreases linearly with inverse lattice edge length. The average occupation probability{\textquoteright}s extrapolated value of 0.608 as the lattice size approaches infinity is found to be a good estimate of the accepted value for the site percolation threshold in two dimensions equal to 0.598.
}, author = {Micielle N Capili and Cristine Villagonzalo and Ronald S. Banzon} } @inproceedings {rodriguez-spp-2007, title = {Crafting a predictor-corrector method}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-068}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
We aim to tailor a predictor-corrector method for an oscillatory-type of solution. The derived method consists of a fourth order predictor and corrector pair. The corrector was chosen from the so-called stability triangle which ensures the method{\textquoteright}s stability. Methods with small errors were chosen as correctors. These correctors were each paired to the already existing Milne-Simpson{\textquoteright}s predictor. The pair with the least error was selected and examined for a simple harmonic oscillator and a damped driven oscillator. The results clearly illustrate the validity of the method for an oscillatory-type of solution since it has reasonably small errors and it was shown to be comparable to the performance of RK4. Our resulting PC4 method has the advantage of less function evaluations, which translates to less error compared to RK4.
}, author = {Mariel Rodriguez and Ronald Banzon} } @inproceedings {pi{\~n}ol-spp-2007, title = {A finite population without imposing the Verhulst factor}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-100}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
The necessity of imposing the concept of a carrying capacity was investigated within the framework of the Penna Model. We find that the number of deaths in a population approaches a saturation point. The carrying capacity {\textendash} Verhulst factor, is the main contributing factor for deaths, over 70\%, in an 8-bit Penna model. Only 3\% and 20\% of the deaths are caused by old age and mutation accumulation, respectively. However, the effect of the common method of accounting for a carrying capacity is diminished as the bit-string length of the Penna Model is decreased. Furthermore, at bit-string length of 2, the Verhulst factor may be removed while still maintaining a finite population.
}, author = {Chrysline Margus Pi{\~n}ol and Ronald S. Banzon} } @inproceedings {gammag-spp-2007, title = {The influence of the level broadening on the chemical potential and the heat capacity of two-dimensional electron system}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-179}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
Experiments on two dimensional electron systems (2DES) in a magnetic field show a broadening of an otherwise delta-like density of states. This broadening has been attributed as an effect of impurity scattering, electron-electron interactions, electron transfers into a reservoir of electronic states, or disorder, among others. As this broadening is usually present in 2DES, this work incorporates the Landau level broadening to have a more realistic electron system. Its effect on the chemical potential and the heat capacity is simulated. Under strong magnetic fields B and fixed electron concentration, both the chemical potential and the heat capacity are found to oscillate with B at constant temperature.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @inproceedings {belisario-spp-2007, title = {Molecular dynamics approach to the reaction rate of composite particles}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-073}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
We present an approach for the determination of the reaction rate of composite particles. We demonstrated that the reaction rate of composite particles may be obtained from the reaction rates of its constituent particles. That is, that the composite particle reaction rate is a function of reaction rates of each individual particles. The use of virtual modelling allowed us to investigate the different configurations of the particles and determine its properties. In this study, a molecular dynamics method was utilized to simulate the behavior of 10 particles moving in a one-dimensional ring. This is done by assuming the particles to be hard spheres interacting via the Lennard-Jones potential. Equilibrium is achieved by reducing the kinetic energy of the particles during a particle-particle collision. A pair is considered to have bonded when their separation distance corresponds to a certain fraction of the minimum potential energy. The model shows that as we increase the fractional energy loss between collisions, the time to equilibrium decreases exponentially.
}, author = {Karla V Belisario and Ronald S. Banzon} } @inproceedings {antonio-spp-2007, title = {Parameter estimates for a reaction rate model}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-101}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
A model for chemical reaction rates that relies solely on the depth of any potential-well function and two parameters intrinsic to the model, A and f, was previously proposed. This study aims to show that using that model, the experimental reaction rate constant can be replicated by simply scaling these two parameters and choosing the proper period to calculate the rate constant, k. It was shown that k is best calculated for the period t4-t2 and for A = 0.01 and f = 0.25 where the \% error is 1.38\%.
}, author = {Kristine Eia S Antonio and Ronald S. Banzon} } @inproceedings {villagonzalo-spp-2007, title = {Reduction of the thermal conductivity in a 1D superlattice}, booktitle = {Proceedings of the 25th Samahang Pisika ng Pilipinas Physics Congress}, year = {2007}, month = {24{\textendash}26 Oct 2007}, pages = {SPP-2007-022}, address = {University of the Phlippines Los Ba{\~n}os, Laguna}, abstract = {
Many technological applications require solids having very low thermal conductivity. This work demonstrates that this can be achieved for specific layer parameters in a superlattice. The phonon dispersion for thick or uneven layered superlattices is modeled using the harmonic approximation in one dimension (1D). The dispersion curves for superlattices with uneven thickness in layers are characterized by the disappearance of forbidden regions. These gaps are usually found in superlattices having uniform thickness. From these results and assuming a constant phonon mean free path, a marked decrease in the lattice contribution to the thermal conductivity is obtained as a function of layer thickness, mass ratio between the layers or asymmetry in its structure.
}, author = {Cristine Villagonzalo and Jane Dizon} } @inproceedings {mandingiado-spp-2006, title = {Complexity in competitive populations}, booktitle = {Proceedings of the 24th Samahang Pisika ng Pilipinas Physics Congress}, year = {2006}, month = {25{\textendash}27 Oct 2006}, pages = {SPP-2006-61}, address = {Ateneo de Davao University, Davao City}, abstract = {
Our results suggest that a more complex strategy for survival is favored in a competitive environment. The degree of complexity is associated with the estimated embedding dimension for population sets where the birth rate, b, and mutation threshold, th, are independently varied. The embedding dimension for a time series determined by parameters of the Penna model was estimated from a simplex projection method. A deviation was encountered, however, for population sets where the maximum number of offspring in a lifetime, max_off, is varied. It is presumed that this may be due to the coupling of the parameters b and the minimum reproductive age r.
}, author = {Ralph Paolo V Mandingiado and Stephanie B Ibo and Ronald S. Banzon} } @article {Paraan2006, title = {Exact moments in a continuous time random walk with complete memory of its history}, journal = {Phys. Rev. E}, volume = {74}, number = {3}, year = {2006}, pages = {032101}, abstract = {
We present a continuous time generalization of a random walk with complete memory of its history [Phys. Rev. E 70, 045101(R) (2004)] and derive exact expressions for the first four moments of the distribution of displacement when the number of steps is Poisson distributed. We analyze the asymptotic behavior of the normalized third and fourth cumulants and identify new transitions in a parameter regime where the random walk exhibits superdiffusion. These transitions, which are also present in the discrete time case, arise from the memory of the process and are not reproduced by Fokker-Planck approximations to the evolution equation of this random walk.
}, doi = {10.1103/PhysRevE.74.032101}, url = {https://journals.aps.org/pre/abstract/10.1103/PhysRevE.74.032101}, author = {Francis N. C. Paraan and Jose Perico Esguerra} } @inproceedings {villagonzalo-spp-2006, title = {A finite temperature magnetic phase transition in a one-dimensional lattice}, booktitle = {Proceedings of the 24th Samahang Pisika ng Pilipinas Physics Congress}, year = {2006}, month = {25{\textendash}27 Oct 2006}, pages = {SPP-2006-155}, address = {Ateneo de Davao University, Davao City}, abstract = {
The effects of a long-range interaction on the magnetization and the heat capacity of a one-dimensional (1D) magnetic ring is studied. In this work, the Monte Carlo method is employed to obtain the equilibrium state of a modified 1D Ising model in a ring geometry having a dipolar interaction of strength G between spins. For a ring consisting of ten spins, the critical temperature at which an ordered state is achieved increases with the absolute value of the dipolar strength. A peak in the heat capacity is observed at finite temperatures. Depending on the magnitude of G, a phase transition at finite temperature may occur.
}, author = {Cristine Villagonzalo and Gina Rose Tongco} } @inproceedings {villagonzalo-spp-2006, title = {Heat capacity of logistic maps with bidirectional coupling}, booktitle = {Proceedings of the 24th Samahang Pisika ng Pilipinas Physics Congress}, year = {2006}, month = {25{\textendash}27 Oct 2006}, pages = {SPP-2006-22}, address = {Ateneo de Davao University, Davao City}, abstract = {
The energy spectra and the heat capacity of two bidirectionally coupled logistics maps obtained from direct numerical simulations are presented. Varying the coupling strength changes the onset of chaos in both maps. In some cases, synchronization in the orbits and heat capacity oscillations of coupled maps are also observed. It is found that the logarithmic-periodic oscillations in the heat capacity of uncoupled logistic maps are no longer observed upon introduction of dissipative coupling.
}, author = {Cristine Villagonzalo and Razel Flores} } @inproceedings {belisario-spp-2006, title = {The molecular dynamics of two particles on a ring}, booktitle = {Proceedings of the 24th Samahang Pisika ng Pilipinas Physics Congress}, year = {2006}, month = {25{\textendash}27 Oct 2006}, pages = {SPP-2006-68}, address = {Ateneo de Davao University, Davao City}, abstract = {
We consider the behavior of two particles on a one-dimensional ring interacting via the Lennard-Jones potential. A collision occurs when the distance between the particles falls within a range corresponding to the minimum potential energy of the system. Equilibrium is achieved when the kinetic energy, which is reduced to an amount proportional to the square of the velocity during particle-particle collision, is less than a fraction of the minimum potential energy. The model shows that as we increase the range in which the Lennard Jones potential is allowed to act on the system, the time needed to achieve equilibrium also increases.
}, author = {Karla V Belisario and Elise Agra and Kristine Eia S Antonio and Ronald S. Banzon} } @inproceedings {antonio-spp-2006, title = {Particle density dependence of molecular dynamics estimated reaction rates}, booktitle = {Proceedings of the 24th Samahang Pisika ng Pilipinas Physics Congress}, year = {2006}, month = {25{\textendash}27 Oct 2006}, pages = {SPP-2006-72}, address = {Ateneo de Davao University, Davao City}, abstract = {
The dependence of the rate of reaction on the particle density of a one-dimensional gaseous system was investigated using molecular dynamics. The particle density in the system was changed by changing the size of the particles, the length of the system, and the number of particles in the system. It was found that, in general, as particle density increased, the rate of the reaction for a system that forms diatomic molecules increased. It was also shown that as the initial kinetic energy of the particles as denoted by the speed was increased, the rate of the reaction increased as well. These findings agree with empirical observations.
}, author = {Kristine Eia S Antonio and Ronald Banzon} } @inproceedings {gammag-spp-2006, title = {Thermodynamic properties of a two-dimensional electron gas in the fractional quantum Hall regime}, booktitle = {Proceedings of the 24th Samahang Pisika ng Pilipinas Physics Congress}, year = {2006}, month = {25{\textendash}27 Oct 2006}, pages = {SPP-2006-69}, address = {Ateneo de Davao University, Davao City}, abstract = {
We investigate the chemical potential μ and specific heat CV of a two-dimensional electron gas at temperatures T\<1 K subject to high magnetic fields B that correspond to filling factors ν\<1. We found out that at ν=1/2, the chemical potential is pinned at ℏω_c/2 which is equal to the energy of the first Landau level. The μ(T) increases when ν\>1/2 and decreases when ν\<1/2. This behavior is dictated by the change in the number of states available to the electrons. We also found out that μ(B) converged at ℏω_c/2 and this trend has a negligible T-dependence. When this behavior of the chemical potential was used in calculating the specific heat at the fractional quantum Hall filling factors, CV(T) exhibited a humpy behavior as compared to its smoothly increasing trend at the integral quantum Hall regime. This trend is a direct consequence of the discontinuities in the chemical potential.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @inproceedings {vasquez-spp-2005, title = {Constant perturbation in the tight-binding bands of a single-walled carbon nanotube}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-019}, address = {Central Philippine University, Iloilo City}, abstract = {
Using a tight-binding calculation, we explain the origin of a large thermopower S in ropes of single-walled carbon nanotubes. We have shown that, by breaking the symmetric energy bands and increasing the overlap energy γ0, a larger S can be obtained. We have also found that a 10\% increase in γ0 resulted to a thermopower that is four times as large.
}, author = {Louella Judy Vasquez and Cristine Villagonzalo} } @inproceedings {jaramillo-spp-2005, title = {Constrained percolation in two dimensions}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-130}, address = {Central Philippine University, Iloilo City}, abstract = {
The effect of implanting square lattice sites of zero occupation probability at the center of a finite but large square lattice for site percolation was investigated. The introduction of symmetrical forbidden site lattices of different sizes inside 40x40 and 60x60 lattices yield percolation threshold values increasing with the size of the forbidden lattice. It was shown that topology in two dimensions dictates the value of the percolation threshold.
}, author = {Christian Oliver Jaramillo and Cristine Villagonzalo and Ronald Banzon} } @inproceedings {delatorre-spp-2005, title = {Finite difference scheme for hyperbolic heat conduction with continuous and pulsed heat sources}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-015}, address = {Central Philippine University, Iloilo City}, abstract = {
The temperature distribution in a region of a one dimensional (1D) semi-infinite slab as defined by the hyperbolic heat equation, is modelled by utilizing the finite-difference approximation for partial-differential equations. The distribution is observed for both pulsed and continuous heat sources for a homogenous medium. The stability of the numerical scheme is determined via the Von-Neumann stability criteria.
}, author = {de la Torre, Agatha and Cristine Villagonzalo} } @inproceedings {gammag-spp-2005, title = {Magnetic field effects on the chemical potential and specific heat of a 2DEG}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-040}, address = {Central Philippine University, Iloilo City}, abstract = {
We investigate the effect of the filling factors on the chemical potential and the specific heat of a two-dimensional electron gas in an external magnetic field. At integer and half-integer filling factors ν the chemical potential is found to jump with an increment of ℏω_c from one Landau level to the next as the magnetic field is increased. In between these special ν{\textquoteright}s the chemical potential tends to infinitesimally increase or decrease in a stepwise manner. This behavior of the chemical potential, in turn, caused the specific heat to vary its behavior with temperature.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @inproceedings {antonio-spp-2005, title = {A model for molecular reaction rates}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-121}, address = {Central Philippine University, Iloilo City}, abstract = {
We propose a model for the determination of the rate of a chemical reaction using molecular dynamics. This is done by approximating the molecules to be hard spheres interacting via the Lennard-Jones potential. A collision occurs in the event that the particle separation falls within a predetermined collision range. Equilibrium is achieved by reducing the kinetic energy by an amount proportional to the square of the velocity, -Av^2, during particle-particle collision. The model shows that as A\ increases, the time to equilbrium, T, decreases exponentially. On the other hand, it also shows that for increasing particle radius R, T\ increases linearly.
}, author = {Kristine Eia S Antonio and Karla V Belisario and Ronald S. Banzon} } @inproceedings {nicolas-spp-2005, title = {Modelling molecular function via multiple collisions}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-147}, address = {Central Philippine University, Iloilo City}, abstract = {
We propose a molecular dynamics model for molecular formation. We utilize a Lennard-Jones potential for the interaction and introduced an energy loss upon collision to what otherwise would have been completely elastic. Results indicates that the rate of reaction increases as the concentration of the substance increases.
}, author = {Mark Lawrence Nicolas and Ronald S. Banzon} } @inproceedings {beech-spp-2005, title = {Survivability in an 8-bit Penna model}, booktitle = {Proceedings of the 23rd Samahang Pisika ng Pilipinas Physics Congress}, year = {2005}, month = {26{\textendash}28 Oct 2005}, pages = {SPP-2005-111}, address = {Central Philippine University, Iloilo City}, abstract = {
Intraspecific competition was simulated using an 8-bit Penna Model, showing that one would harvest resources, while the other would be driven to extinction. The ability of a population to compete with their coexistent population is largely affected by intrinsic properties that affect the population saturation. Results suggest that it is the high tolerance of mutations and the high maximum number of offspring in a lifetime that describe a more competitive population. Given these parameters to be equal, the population which fluctuates less about the equilibrium population is preferred.
}, author = {Maria Donna N Beech and Ronald S. Banzon} } @inproceedings {vasquez-spp-2004, title = {Diffusive thermoelectric transport in carbon nanotubes}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {119}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {This paper aims to study the diffusion thermoelectric power of singe-walled carbon nanotubes (SWNTs). This was obtained using a linear response method and a semiclassical treatment of metallic-like systems. The energy and the density of states were generated using the tight binding model for both electrons and holes. The SWNT, exhibiting a diffusive transport, is shown to have a negative thermoelectric power for an energy-dependent relaxation time. This indicates that electrons are dominant and demonstrates a metallic-like behavior.}, author = {Louella Judy Vasquez and Cristine Villagonzalo} } @inproceedings {tongco-spp-2004, title = {Dipolar interaction in a 1-D Ising ring}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {31}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
The effects of a long-range interaction in a one-dimensional (1D) magnetic ring is studied. In this work, the Monte Carlo method is employed to obtain the equilibrium state of a modified quasi-1D Ising model having a dipolar interaction in a ring geometry. At low temperatures (T), the behavior of the magnetization (M) as a function of T is shown to depend on the strength of the dipolar interaction (G). For a ring consisting of 10 spins, ferromagnetic states occur in the ground state (T=0) for a small value of G. Antiferromagnetic states are favored when G is large even at a finite temperature. The magnetization saturates at high T. Also, an effective lowering of the total energy is achieved when smaller values of G approach zero and when large value of G is increased further. Similar effects are observed for rings having a larger number of spins.
}, author = {Gina Rose Tongco and Cristine Villagonzalo} } @article {Tongco2004, title = {Dipolar interaction in a one-dimensional Ising ring}, journal = {Science Diliman}, volume = {16}, year = {2004}, pages = {8-9}, abstract = {
As synthesis of low-dimensional magnetic systems become possible, the need for theoretical understanding of their behavior arises. In this work, the authors explore a one-dimensional magnetic structure with the spins having dipolar interaction.
}, url = {http://journals.upd.edu.ph/index.php/sciencediliman/article/view/85}, author = {Gina Rose Tongco and Cristine Villagonzalo} } @inproceedings {marco-spp-2004, title = {Effect of the hopping parameter on the current through a two-atom molecular wire}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {27}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
We utilize the Hubbard model approach in analyzing the effect of the hopping parameter in the transport properties of a two-atom molecular device. A root finding method was utilized to implement self-consistent calculations to obtain the transport properties and our results agree with that in the literature. Variation of the hopping parameter shows that its value is proportional to the threshold voltage in the presence of an on-site Coulomb interaction U.
}, author = {Ronaldo Marco Jr and Ronald S. Banzon and Cristine Villagonzalo} } @article {Morales2004, title = {Enhancement of Fe magnetic moments in Fe/Co (001) multilayers}, journal = {Science Diliman}, volume = {16}, year = {2004}, pages = {6-7}, abstract = {
In order to investigate the electronic and magnetic properties of a bcc Fe/Co (001) multilayer, we have performed electronic structure calculations employing the total energy full-potential linear muffin tin orbital method. The magnetic moments of the layers are calculated. Based on these results, the magnetization profiles and the microscopic origin of the enhancement of Fe moments in the multilayers of the same Co content but with different interface qualities are reported. Large enhancement of magnetic moment is observed in the Fe monolayer located at the interface, and an even greater increase is obtained for the multilayer with one monolayer of intermixing between Fe and Co layers. The Co atoms were found to have similar magnetic moments in the bulk and at the interface.
}, url = {http://journals.upd.edu.ph/index.php/sciencediliman/article/view/84}, author = {Marienette B Morales and Cristine Villagonzalo} } @inproceedings {morales-spp-2004, title = {Enhancement of Fe magnetic moments in Fe/Co(001) multilayer}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {72}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
In order to investigate the electronic and magnetic properties of a bcc Fe/Co (001) multilayer, we have performed electronic structure calculations employing the total energy full-potential linear muffin tin orbital method (FP-LMTO). The magnetic moments of the layers are calculated. Based on these results, the magnetization profiles and the microscopic origin of the enhancement of Fe moments in the multilayers of the same Co content but with different interface quality are reported. Large enhancement of magnetic moment is observed in Fe monolayer located at the interface, and even greater increase is obtained for the multilayer with one monolayer of intermixing between Fe and Co layers. The Co atoms were found to have similar magnetic moments in the bulk and at the interface.
}, author = {Marienette Morales and Cristine Villagonzalo} } @article {Marco2004, title = {Hopping in a molecular wire}, journal = {Science Diliman}, volume = {16}, year = {2004}, pages = {10-11}, abstract = {
We utilize the Hubbard model approach in analyzing the effect of the hopping parameter in the transport properties of a two-atom molecular device.
}, url = {http://journals.upd.edu.ph/index.php/sciencediliman/article/view/86}, author = {Ronaldo Marco Jr and Ronald Banzon and Cristine Villagonzalo} } @inproceedings {beech-spp-2004, title = {Periodicity in a Penna model}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {11}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
A population of an asexually reproducing species is simulated using a suggested 8-bit string length implementation and a modified implementation of the Verhulst factor. The age structure of the population generated by this implementation is found to be non-Gompertzian and time-dependent. The change in age structure is shown to be a result of the periodic behavior of the population of its component ages, with relatively similar period, but different phase.
}, author = {Maria Donna N Beech and Ronald S. Banzon} } @inproceedings {pari{\~n}as-spp-2004, title = {Pre-collision dynamics of short 1D anharmonic chains}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {118}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
This paper investigates the dynamics of short one-dimensional lattices having a temperature gradient. An anharmonic potential using the Fermi-Pasta-Ulam (FPU) model was assumed. Three different systems were studied: a uniform chain, a chain with a single impurity, and a diatomic chain. Numerical simulations using the fourth order Runge-Kutta algorithm was used to solve the equations of motion. An impurity in the chain serves as a {\textquotedblleft}thermal barrier{\textquotedblright}. In the diatomic lattice, an energy excitation is formed even before any particle collision occurs. Here the energy distribution at different times will be shown.
}, author = {Ricelle Pari{\~n}as and Cristine Villagonzalo} } @inproceedings {nombres-spp-2004, title = {Random deaths and chaos in a Penna model}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {54}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
We utilise an 8-bit Penna bit-string model of biological aging in studying the dynamics of an asexually reproducing, single species and non-migrating population using a modified version of the Verhulst death factor. It was seen that different implementations of the death procedure, one that is applied to all the individuals within the population (VA), and one that is applied only to newborns (VB) exhibited some similar, but mostly different dynamical behaviours. It was shown that the VB population has a higher level of chaos as compared to VA. Aside from an increase in the birth rate, B, chaos also resulted from an increase in the mutation threshold, T.
}, author = {Chris Nombres and Ronald S. Banzon} } @inproceedings {gammag-spp-2004, title = {The specific heat of a 2DEG in a magnetic field}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {154}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
We investigate the specific heat of a two-dimensional electron gas (2DEG) and how it varies with the system{\textquoteright}s temperature and chemical potential in the presence of an external magnetic field. In this work, we take into account the dependence of the chemical potential with temperature. We show that the specific heat of the system exhibits a two-peak behavior at low T regardless of the field{\textquoteright}s magnitude if μ~T^2 and that this is consistent with results in the literature where the broadening of Landau levels was considered. The underlying processes may be different but the effect on CV is similar.
}, author = {Rayda P Gammag and Cristine Villagonzalo} } @article {Obias2004, title = {Tempering and annealing in a Verdier-Stockmayer polymer}, journal = {Science Diliman}, volume = {16}, year = {2004}, pages = {12-16}, abstract = {
Two Monte Carlo methods, simulated annealing and parallel tempering, were applied to a Verdier-Stockmayer polymer. The efficiency of the two algorithms in exploring the lowest energy state possible for the model polymers was measured by the number of energy-degenerate configurations (configurations that have the same energy but are structurally different). Parallel tempering consistently explored more energy-degenerate configurations as compared with simulated annealing.
}, url = {http://journals.upd.edu.ph/index.php/sciencediliman/article/view/87}, author = {Eric R Obias and Ronald S. Banzon} } @inproceedings {obias-spp-2004, title = {Tempering and annealing in a Verdier-Stockmayer polymer}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {32}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
Two Monte Carlo methods, simulated annealing and parallel tempering, were applied to a Verdier-Stockmayer polymer. The efficiency of the two algorithms in exploring the lowest energy state possible for the model polymers was measured by the number of energy degenerate configurations (configurations that have the same energy but are structurally different). Parallel tempering consistently explored more energy degenerate configurations as compared to simulated annealing.
}, author = {Eric Bryan Obias and Ronald S. Banzon} } @inproceedings {dizon-spp-2004, title = {Thermal conductivity in a one-dimensional superlattice}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {155}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
We investigate the phonon thermal conductivity in a one-dimensional superlattice for transport perpendicular to the layers by utilizing analytic methods. A reduction on the thermal conductivity was observed when the layer thickness of the superlattice was increased. Difference in the mass ratio of the atoms in the chain and force constant ratio on alternating layers produced variations in the thermal conductivity. Higher difference of either of these two parameters results in the decrease of the thermal conductivity.
}, author = {Jane Dizon and Cristine Villagonzalo} } @inproceedings {muldera-spp-2004, title = {Thermal efficiency of a quasi-one-dimensional conductor}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {113}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
How does a system{\textquoteright}s dimension affect its thermal efficiency? In this work, we will show that if conduction is constrained in a single direction in a three dimensional conductor, it will become more efficient in conducting thermal energy as its width is reduced. Herein, we investigate the electric and thermal properties of a quasi-one-dimensional conductor using the free electron gas model in the relaxation time approximation scheme. This is demonstrated in the wire width dependence of the electric conductivity, thermal conductivity and figure of merit. We will also show the dependence of these transport properties to the system{\textquoteright}s chemical potential.
}, author = {Joselito Muldera and Cristine Villagonzalo} } @inproceedings {sandagon-spp-2004, title = {Variational Monte Carlo of a 2D quantum well system}, booktitle = {Proceedings of the 22nd Samahang Pisika ng Pilipinas Physics Congress}, year = {2004}, month = {25{\textendash}27 Oct 2004}, pages = {153}, address = {Bohol Tropics Resort, Tagbilaran City}, abstract = {
The convergence of a Variational Monte Carlo method with Gaussian importance sampling (VMC-GIS), as applied to a two-dimensional time-independent quantum well, was improved by optimizing the standard deviation σ of the Gaussian probability distribution. The fastest convergence in attaining the ground state is obtained by using VMC-GIS with σ=0.6 .
}, author = {Ryan Sandagon and Ronald S. Banzon and Cristine Villagonzalo} } @inproceedings {labora-spp-2003, title = {Ab-initio structural investigation of Fe/V (001) multilayers}, booktitle = {Proceedings of the 21st Samahang Pisika ng Pilipinas Physics Congress}, year = {2003}, month = {22{\textendash}25 Oct 2003}, pages = {SPP-2003-1D-02}, address = {University of San Carlos, Cebu City}, abstract = {The structural properties of Fe/V multilayers are studied using electronic structure calculations. A first principle numerical calculation is implemented using the Full Potential Linear Muffin-Tin (FPLMTO) method based on the Density Functional Theory (DFT). The number of Fe and V in a Fe/V supercell is varied while the total atoms is kept constant. The energetically equilibrium structure of this multilayer is presented. Two types of multilayer structures, the Fe-on-V and the V-on-Fe, are investigated and compared to bulk values and reported experimental results. Results show that the total energy for Fe-on-V multilayer gives a lower value compared to V-on-Fe multilayer signifying that the V-on-Fe is a more stable structure than Fe-on-V, a result which is consistent with experimental observations. The simple case of the effect of intermixing is presented and its total energy and spin moment is compared to the bulk value.}, url = {https://proceedings.spp-online.org/article/view/SPP-2003-1D-02}, author = {Marites Labora and Cristine Villagonzalo} } @inproceedings {morales-spp-2003, title = {Magnetization and magnetic anisotropy of Fe/Co multilayers: A first-principles calculation}, booktitle = {Proceedings of the 21st Samahang Pisika ng Pilipinas Physics Congress}, year = {2003}, month = {22{\textendash}25 Oct 2003}, pages = {SPP-2003-PB-05}, address = {University of San Carlos, Cebu City}, abstract = {The magnetic properties of bcc Fe/Co (001) multilayers are calculated from first-principles by means of the full potential linear muffin tin orbital method (FLMTO). A significant enhancement in the magnetic moments of each atom in the multilayer is observed. The magnetization and magnetic anisotropy energy MAE are described as a function of Fe/Co layer thickness ratio. For comparison with the obtained multilayer values, the magnetization and MAE of constituent atoms, bcc Co bulk are also verified. The results for the magnetization and MAE agree well with experimental results.}, url = {https://proceedings.spp-online.org/article/view/SPP-2003-PB-05}, author = {Marienette B Morales and Cristine Villagonzalo} } @inproceedings {villagonzalo-spp-2003, title = {Numerical investigations on the growth textures of Co/Cu multilayers}, booktitle = {Proceedings of the 21st Samahang Pisika ng Pilipinas Physics Congress}, year = {2003}, month = {22{\textendash}25 Oct 2003}, pages = {SPP-2003-3D-01}, address = {University of San Carlos, Cebu City}, abstract = {A first-principles investigation on the growth textures of cobalt/copper multilayers is presented. Through an ab-initio local-density approximation in a full-potenatial linear muffin-tin orbital (FPLMTO) electronic structure method, the different growth textures of Co/Cu multilayers are compared. Through total energy minimization, the face-centered cubic (111) configuration is determined to be the preferred textural orientation as compared to the (110) and (001) directions. Physically, this suggests that (111) configuration is more favorable to grow. Included in this report are results of intermixing Co/Cu interfaces which verifies that Co and Cu are immiscible in the bulk. This work provides a benchmark for thermal transport studies in multilayers.}, url = {https://proceedings.spp-online.org/article/view/SPP-2003-3D-01}, author = {Cristine Villagonzalo and Arun K Setty and Bernard R Cooper} } @article {R{\"o}mer2003167, title = {Thermoelectric properties of disordered systems}, journal = {J. Phys. Soc. Jpn. Suppl. A}, volume = {72}, number = {SUPPL. A}, year = {2003}, pages = {167-168}, abstract = {
The electronic properties of disordered systems have been the subject of intense study for several decades. Thermoelectric properties, such as thermopower and thermal conductivity, have been relatively neglected. A long standing problem is represented by the sign of the thermoelectric power. In crystalline semiconductors this is related to the sign of the majority carriers, but in non-crystalline systems it is commonly observed to change sign at low temperatures. In spite of its apparent universality this change has been interpreted in a variety of ways in different systems. We have developed a Green{\textquoteright}s function recursion algorithm based on the Chester-Thelling-Kubo-Greenwood formula for calculating the kinetic coefficients on long strips or bars. From these we can deduce the electrical conductivity, the Seebeck and Peltier coefficients and the thermal conductivity, as well as the Lorenz number. We present initial results for 1D systems. We observe a Lorentzian distribution for the thermopower which is modified by the presence of inelastic scattering. This could give rise to non-negligible quantum fluctuations in macroscopic systems at low temperatures.
}, doi = {10.1143/JPSJS.72SA.167}, author = {Rudolf A R{\"o}mer and Angus MacKinnon and Cristine Villagonzalo} } @article {Villagonzalo200016446, title = {Behavior of the thermopower in amorphous materials at the metal-insulator transition}, journal = {Phys. Rev. B}, volume = {62}, number = {24}, year = {2000}, note = {cited By 4}, pages = {16446-16452}, abstract = {
We study the behavior of the thermal transport properties in three-dimensional disordered systems close to the metal-insulator transition within linear response. Using a suitable form for the energy-dependent conductivity σ, we show that the value of the dynamical scaling exponent for noninteracting disordered systems such as the Anderson model of localization can be reproduced. Furthermore, the values of the thermopower S have the right order of magnitude close to the transition as compared to the experimental results. A sign change in the thermoelectric power S {\textemdash} as is often observed in experiments {\textemdash} can also be modeled within the linear response formulation using modified experimental σ data as input.
}, doi = {10.1103/PhysRevB.62.16446}, author = {Cristine Villagonzalo and Rudolf A R{\"o}mer and Michael Schreiber and Angus MacKinnon} } @article {Villagonzalo1999179, title = {Thermoelectric transport properties in disordered systems near the Anderson transition}, journal = {Eur. Phys. J. B}, volume = {12}, number = {2}, year = {1999}, note = {cited By 12}, pages = {179-189}, abstract = {
We study the thermoelectric transport properties in the three-dimensional Anderson model of localization near the metal-insulator transition (MIT). In particular, we investigate the dependence of the thermoelectric power S, the thermal conductivity K, and the Lorenz number L0 on temperature T. We first calculate the T dependence of the chemical potential μ from the number density n of electrons at the MIT using an averaged density of states obtained by diagonalization. Without any additional approximation, we determine from the behavior of S, K and L0 at low T as the MIT is approached. We find that the d.c. conductivity and K decrease to zero at the MIT as T -\> 0 and show that S does not diverge. Both S and L0 become temperature independent at the MIT and depend only on the critical behavior of the conductivity.
}, doi = {10.1007/s100510050994}, author = {Cristine Villagonzalo and Rudolf A R{\"o}mer and Michael Schreiber} } @article {Villagonzalo1998394, title = {Low temperature behavior of the thermopower in disordered systems near the Anderson transition}, journal = {Ann. Phys. (Leipzig)}, volume = {7}, number = {5-6}, year = {1998}, note = {cited By 5}, pages = {394-399}, abstract = {
We investigate the behavior of the thermoelectric power S in disordered systems close to the Anderson-type metal-insulator transition (MIT) at low temperatures. In the literature, we find contradictory results for S. It is either argued to diverge or to remain a constant as the MIT is approached. To resolve this dilemma, we calculate the number density of electrons at the MIT in disordered systems using an averaged density of states obtained by diagonalizing the three-dimensional Anderson model of localization. From the number density we obtain the temperature dependence of the chemical potential necessary to solve for S. Without any additional approximation, we use the Chester-Thellung-Kubo-Greenwood formulation and numerically obtain the behavior of S at low T as the Anderson transition is approached from the metallic side. We show that indeed S does not diverge.
}, doi = {10.1002/(SICI)1521-3889(199811)7:5/6<394::AID-ANDP394>3.0.CO;2-Q}, author = {Cristine Villagonzalo and Rudolf A R{\"o}mer} }