@inproceedings {712,
	title = {Dynamics of an open quantum Otto engine with a working substance in a harmonic oscillator potential well},
	booktitle = {Proceedings of the 43rd Samahang Pisika ng Pilipinas Physics Conference},
	year = {2025},
	month = {25{\textendash}28 Jun 2025},
	pages = {SPP-2025-1D-06},
	address = {Quezon City},
	abstract = {This study investigates the performance of an open system quantum Otto heat engine, whose working medium consists of particles confined in a harmonic oscillator potential. The expansion and compression of this system is controlled by the frequency of the oscillator. Thermal energy is transferred from the heat baths connected to the isochoric branches. The dynamical trajectories were plotted for each thermodynamic step and the work done by the engine was calculated. From the ratio of the useful work and input heat, we obtain the efficiency when the working substance consists of either bosons or fermions. Here bosons are found to be more efficient as they allow multiple occupancy of states.},
	url = {https://proceedings.spp-online.org/article/view/SPP-2025-1D-06},
	author = {Gene Michael P. Herman and Cristine D. Villagonzalo}
}
@conference {699,
	title = {Thermodynamics performance optimization of a Lipkin-Meshkov-Glick heat engine model with anisotropy},
	year = {2024},
	month = {10{\textendash}16 Nov 2024},
	publisher = {Asian Network School and Workshop on Complex Condensed Matter Systems 2024},
	address = {Chulalongkorn University, Bangkok and Suranaree University of Technology, Nakhon Ratchasima},
	abstract = {Heat engine implementation in the atomic or nanoscale involves thermodynamic and quantum properties of the working substance. Interest in the optimization of these quantum effects is driven by the rise of electronic devices in the nanoscale and the search for devices that can power quantum technologies in the future. It has been shown that quantum heat engines outperform their classical counterparts, and several physically realizable engines have been constructed using quantized spin models. We investigate the performance of the quantum heat engine following a Carnot cycle with four strokes {\textendash} two reversible isothermal and isomagnetic steps, connected to constant temperature heat baths. The working medium of this quantum device is the Lipkin-Meshkov-Glick (LMG) model consists of two or three spins. In this work, anisotropy is introduced to the working medium. The energy eigenstates are calculated by solving Schr{\"o}dinger{\textquoteright}s equation and the thermodynamic performance of each process is obtained using the canonical ensemble. The effect of anisotropy in the operation of the engine is seen in the energy eigenvalues as work production is maximized for specific anisotropy and applied magnetic field strengths. Optimization of the applied magnetic field for a given anisotropy and the change in the adjacent energy level spacing determines the efficiency of a quantum Carnot heat engine.},
	url = {https://indico.cern.ch/event/1450400/},
	author = {Gene Michael P. Herman and Cristine D. Villagonzalo}
}
@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}
}
@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}
}