Quantum spin Hall effect and topological phase transition in two-dimensional square transition-metal dichalcogenides
Quantum spin Hall effect and topological phase transition in two-dimensional square transition-metal dichalcogenides
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DOI：
10.1103/physrevb.92.085427
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发表时间：
2015-08-25
影响因子：
3.7
通讯作者：
Heine, Thomas
中科院分区：
文献类型：
--
作者：
Ma, Yandong;Kou, Liangzhi;Heine, Thomas
基于二维拓扑绝缘体的边缘电子态的传播方向被锁定在其自旋取向上的事实，二维拓扑绝缘体在自旋电子学中具有很好的应用前景。在这里，我们用第一性原理计算，预测了单层正方形过渡金属二卤化物MX2(M=Mo，W；X=S，Se，Te)中的一族强健的2D TIS，它们的本征禁带宽度从24 meV到187 meV，从而保证了室温下的量子自旋霍尔效应。与已知的具有可比带隙的2D TI不同，这些较大的能隙来自与Mo/W原子的d电子相关的强烈的自旋-轨道相互作用。在这些系统的边缘出现了一对受拓扑保护的螺旋边缘态，在体带隙内具有狄拉克类型的色散。用非平凡的Z(2)型拓扑不变量证明了拓扑的非平凡性质。更有趣的是，在外加应变的情况下，可以实现QSH相和平凡的绝缘/金属相之间的拓扑量子相变，并很好地建立了相应的拓扑相图。
Two-dimensional (2D) topological insulators (TIs) hold promise for applications in spintronics based on the fact that the propagation direction of an edge electronic state of a 2D TI is locked to its spin orientation. Here, using first-principles calculations, we predict a family of robust 2D TIs in monolayer square transition-metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te), which show sizeable intrinsic nontrivial band gaps ranged from 24 to 187 meV, thus ensuring the quantum spin Hall (QSH) effect at room temperature. Different from the most known 2D TIs with comparable band gaps, these sizeable energy gaps arise from the strong spin-orbit interaction related to d electrons of the Mo/W atoms. A pair of topologically protected helical edge states emerges at the edge of these systems with a Dirac-type dispersion within the bulk band gap. The topologically nontrivial natures are confirmed by the nontrivial Z(2)-type topological invariant. More interestingly, with applied strain, a topological quantum phase transition between a QSH phase and a trivial insulating/metallic phase can be realized, and the corresponding topological phase diagram is well established.