On the Quantum Spin Hall Gap of Monolayer 1T '-WTe2
On the Quantum Spin Hall Gap of Monolayer 1T '-WTe2
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DOI：
10.1002/adma.201600100
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发表时间：
2016
影响因子：
29.4
通讯作者：
Feng Ji
中科院分区：
文献类型：
--
作者：
Zheng Feipeng;Cai Chaoyi;Ge Shaofeng;Zhang Xuefeng;Liu Xin;Lu Hong;Zhang Yudao;Qiu Jun;Taniguchi Takashi;Watanabe Kenji;Jia Shuang;Qi Jingshan;Chen Jian-Hao;Sun Dong;Feng Ji
量子自旋霍尔（QSH）材料是同时具有绝缘体态和螺旋边态的二维系统。一个QSH绝缘体处理拓扑非平凡的边缘状态保护的时间反演对称性，使电子可以传播无散射。这种拓扑相的实现在自旋电子学、无耗散输运和量子计算中有着广阔的应用前景。目前，这种基于QSH的器件的实现仅限于复杂的异质结构。单层1 T '-WTe 2被预测为半金属QSH材料，但具有负带隙。用混合泛函方法得到的准粒子能谱直接表明，单层1 T '-WTe 2的量子自旋霍尔能隙为正。光学测量显示，随着层数的减少，带间弛豫时间系统性增加，而输运测量显示超薄样品中的肖茨基势垒，而较厚的样品则不存在这种势垒。这三个独立的证据表明，单层1 T '-WTe 2可能是一个真正的二维量子自旋霍尔绝缘体。
Quantum spin Hall (QSH) materials are two-dimensional systems exhibiting insulating bulk and helical edge states simultaneously. A QSH insulator processes topologically non-trivial edge states protected by time-reversal symmetry, so that electrons can propagate unscattered. Realization of such topological phases enables promising applications in spintronics, dissipationless transport and quantum computations. Presently, realization of such QSH-based devices are limited to complicated heterostructures. Monolayer 1T'-WTe2 was predicted to be semimetallic QSH materials, though with a negative band gap. The quasi-particle spectrum obtained using hybrid functional approach shows directly that the quantum spin Hall gap is positive for monolayer 1T'-WTe2. Optical measurement shows a systematic increase in the interband relaxation time with decreasing number of layers, whereas transport measurement reveals Schottcky barrier in ultrathin samples, which is absent for thicker samples. These three independent pieces of evidence indicate that monolayer 1T'-WTe2 is likely a truly 2-dimensional quantum spin Hall insulator.