Center for Applied Physics and Technology, College of Engineering, Peking University; Key Laboratory of High Energy Density Physics Simulation, Ministry of Education, Beijing 100871, China.
Nanoscale. 2017 Jan 5;9(2):562-569. doi: 10.1039/c6nr07851f.
First-principles calculations and extensive analyses reveal that the H phase of two-dimensional (2D) transition metal dichalcogenides (TMDs) can be tuned to topological insulators by introducing square-octagon (4-8) defects and by applying equi-biaxial tensile strain simultaneously. The 2D structure composed of hexagonal rings with 4-8 defects, named sho-TMD, is dynamically and thermally stable. The critical equi-biaxial tensile strain for the topological phase transition is 4%, 6%, and 4% for sho-MoS, sho-MoSe and sho-WS, respectively, and the corresponding nontrivial band gap induced by the spin-orbit coupling is 2, 8, and 22 meV, implying the possibility of observing the helical conducting edge states that are free of backscattering in experiment. It is equally interesting that the size of the energy band gap of the H-phase can be flexibly tuned by changing the concentration of 4-8 defects while the feature of the quasi-direct band gap semiconductor remains. These findings add additional traits to the TMD family, and provide a new strategy for engineering the electronic structure and the band topology of 2D TMDs for applications in nanoelectronics and spintronics.
第一性原理计算和广泛分析表明，通过引入正方形-八边形（4-8）缺陷并同时施加等双轴拉伸应变，二维（2D）过渡金属二硫属化物（TMD）的 H 相可以被调谐为拓扑绝缘体。由具有 4-8 缺陷的六边形环组成的 2D 结构，命名为 sho-TMD，在动力学和热力学上是稳定的。拓扑相变的临界等双轴拉伸应变为 sho-MoS、sho-MoSe 和 sho-WS 分别为 4%、6%和 4%，由自旋轨道耦合引起的非平凡带隙分别为 2、8 和 22meV，这意味着在实验中观察到无背散射的螺旋传导边缘态是可能的。同样有趣的是，通过改变 4-8 缺陷的浓度可以灵活地调节 H 相的能带隙大小，而准直接带隙半导体的特性仍然存在。这些发现为 TMD 家族增添了新的特性，并为工程 2D TMD 的电子结构和能带拓扑提供了新的策略，以应用于纳米电子学和自旋电子学。
