Liying Ouyang | Searcharxiv

arXiv2019

Alloying-induced topological transition in 2D transition-metal dichalcogenide semiconductors

Research on two-dimensional (2D) topological insulators (TIs) is obstructed due to the lack of feasible approaches to growing 2D TIs in experiments. Through systematic first-principles calculations and tight-binding simulations, we propose that alloying Os in 2D MoX2 (X = S, Se, Te) monolayers is an effective approach to inducing semiconductor-to-TI transitions, with sizable nontrivial gaps of 25-37 meV. Analysis of the electronic structures reveals that the topological property mainly originates from the 5d orbitals of the Os atom. Furthermore, the TI gaps can be modulated by external biaxial strain.

cond-mat.mtrl-sci↗

arXiv2018

Realizing robust large-gap quantum spin Hall state in 2D HgTe monolayer on insulating substrate

Although many possible two-dimensional (2D) topological insulators (TIs) have been predicted in recent years, there is still lack of experimentally realizable 2D TI. Through first-principles and tight-binding simulations, we found an effective way to stabilize the robust quantum spin Hall state with a large nontrivial gap of 227 meV in 2D honeycomb HgTe monolayer by the Al$_2$O$_3$(0001) substrate. The band topology originates from the band inversion between the $s-$like and $p-$like orbitals that are contributed completely by the Hg and Te atoms, so the quantized edge states are restricted within the honeycomb HgTe monolayer. Meanwhile, the strong interaction between HgTe and Al$_2$O$_3$(0001) ensures high stability of the atomic structure. Therefore, the TI states may be realized in HgTe/Al$_2$O$_3$(0001) at high temperature.

cond-mat.mtrl-sci↗