Determination of the Spin Axis in Quantum Spin Hall Insulator Candidate Monolayer WTe2
Determination of the Spin Axis in Quantum Spin Hall Insulator Candidate Monolayer WTe2
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DOI：
10.1103/physrevx.11.041034
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发表时间：
2020-10
影响因子：
12.5
通讯作者：
Wenxuan Zhao;E. Runburg;Z. Fei;J. Mutch;P. Malinowski;Bosong Sun;Xiong Huang;D. Pesin;
中科院分区：
文献类型：
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作者：
Wenxuan Zhao;E. Runburg;Z. Fei;J. Mutch;P. Malinowski;Bosong Sun;Xiong Huang;D. Pesin;
量子自旋霍尔（QSH）效应的证据已经在几个实验系统中以近似量子化的边缘电导的形式报道。然而，QSH效应的最基本特征，即边缘通道中的自旋动量锁定，从未在实验上得到证实。在这里，我们报告了单层WTe 2的边缘通道中的自旋动量锁定的明确证据，WTe 2被认为是二维拓扑绝缘体（2D TI）。我们观察到，边缘电导是由垂直于一个特定的轴，我们确定为自旋轴的施加磁场的分量控制。所有边缘的轴都是相同的，位于垂直于钨链的镜面上，与层法线成40 ± 2°，这意味着自旋轨道耦合是从体能带结构继承的。我们表明，这一发现是与理论相一致的，如果带边轨道采取有喜欢的宇称。我们的结论是，这种宇称分配是正确的，在单层WTe 2的边缘状态和散装带共享相同的简单的自旋结构。结合边缘状态的其他已知特征，这建立了自旋动量锁定，因此单层WTe 2是真正的天然2D TI。
Evidence for the quantum spin Hall (QSH) effect has been reported in several experimental systems in the form of approximately quantized edge conductance. However, the most fundamental feature of the QSH effect, spin-momentum locking in the edge channels, has never been demonstrated experimentally. Here, we report clear evidence for spin-momentum locking in the edge channels of monolayer WTe2, thought to be a two-dimensional topological insulator (2D TI). We observe that the edge conductance is controlled by the component of an applied magnetic field perpendicular to a particular axis, which we identify as the spin axis. The axis is the same for all edges, situated in the mirror plane perpendicular to the tungsten chains at 40 ± 2° to the layer normal, implying that the spin-orbit coupling is inherited from the bulk band structure. We show that this finding is consistent with theory if the band-edge orbitals are taken to have like parity. We conclude that this parity assignment is correct and that both edge states and bulk bands in monolayer WTe2 share the same simple spin structure. Combined with other known features of the edge states this establishes spinmomentum locking, and therefore that monolayer WTe2 is truly a natural 2D TI.