@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 M. Macam and Yifan Gao and Naga Venkateswara Rao Nulakani and Xun Ge and Xiang Ye and Feng-Chuan Chuang and Li Huang}
}
@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}
}
@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}
}