title: Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe.
abstract: Two-dimensional (2D) topological insulators (TIs) with large band gaps are of great importance for the future applications of quantum spin Hall (QSH) effect. Employing ab initio electronic calculations we propose a novel type of 2D topological insulators, the monolayer (ML) low-buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gap. We demonstrate that LB HgTe (HgSe) monolayers undergo a trivial insulator to topological insulator transition under in-plane tensile strain of 2.6% (3.1%) due to the combination of the strain and the spin orbital coupling (SOC) effects. Furthermore, the band gaps can be tuned up to large values (0.2 eV for HgTe and 0.05 eV for HgSe) by tensile strain, which far exceed those of current experimentally realized 2D quantum spin Hall insulators. Our results suggest a new type of material suitable for practical applications of 2D TI at room-temperature.
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Jin
authors.initials: J
authors.lastname: Li
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Chaoyu
authors.initials: C
authors.lastname: He
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Meng
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Huaping
authors.initials: H
authors.lastname: Xiao
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Chao
authors.initials: C
authors.lastname: Tang
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Wei
authors.affiliation: Department of Physics, California State University, Northridge, California 91330-8268, USA.
authors.forename: Jinwoong
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Physics, California State University, Northridge, California 91330-8268, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Kioussis
authors.affiliation: Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: G Malcolm
authors.initials: GM
authors.lastname: Stocks
authors.affiliation: Hunan Key Laboratory of Micro-Nano Energy Materials and Devices, Xiangtan University, Hunan 411105, P. R. China.|Laboratory for Quantum Engineering and Micro-Nano Energy Technology and School of Physics and Optoelectronics, Xiangtan University, Hunan 411105, P. R. China.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Zhong