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arXiv · 1401.4100

Functionalized Germanene as a Prototype of Large-Gap Two-Dimensional Topological Insulators

Chen Si·Junwei Liu·Yong Xu·Jian Wu·Bing-Lin Gu·Wenhui Duan
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Abstract

We propose new two-dimensional (2D) topological insulators (TIs) in functionalized germanenes (GeX, X=H, F, Cl, Br or I) using first-principles calculations. We find GeI is a 2D TI with a bulk gap of about 0.3 eV, while GeH, GeF, GeCl and GeBr can be transformed into TIs with sizeable gaps under achievable tensile strains. A unique mechanism is revealed to be responsible for large topologically-nontrivial gap obtained: owing to the functionalization, the $\sigma$ orbitals with stronger spin-orbit coupling (SOC) dominate the states around the Fermi level, instead of original $\pi$ orbitals with weaker SOC; thereinto, the coupling of the $p_{xy}$ orbitals of Ge and heavy halogens in forming the $\sigma$ orbitals also plays a key role in the further enlargement of the gaps in halogenated germanenes. Our results suggest a realistic possibility for the utilization of topological effects at room temperature.

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Chen Si, Junwei Liu, Yong Xu, Jian Wu, Bing-Lin Gu, Wenhui Duan. 2014-01-16. Functionalized Germanene as a Prototype of Large-Gap Two-Dimensional Topological Insulators. https://doi.org/10.1103/physrevb.89.115429

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