在时间反演对称性破缺情况下碲化汞量子阱中的意外边缘传导
Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry.
作者信息
Ma Eric Yue, Calvo M Reyes, Wang Jing, Lian Biao, Mühlbauer Mathias, Brüne Christoph, Cui Yong-Tao, Lai Keji, Kundhikanjana Worasom, Yang Yongliang, Baenninger Matthias, König Markus, Ames Christopher, Buhmann Hartmut, Leubner Philipp, Molenkamp Laurens W, Zhang Shou-Cheng, Goldhaber-Gordon David, Kelly Michael A, Shen Zhi-Xun
机构信息
1] Geballe Laboratory for Advanced Materials, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA [2] Department of Applied Physics, Stanford University, 348 Via Pueblo Mall, Stanford, California 94305, USA.
1] Geballe Laboratory for Advanced Materials, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA [2] Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, USA.
出版信息
Nat Commun. 2015 May 26;6:7252. doi: 10.1038/ncomms8252.
The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy, and compare our findings to a non-inverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. This indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.
HgTe量子阱中量子自旋霍尔效应的实现被认为是拓扑绝缘体发现过程中的一个里程碑。如各种实验所示，量子自旋霍尔态预计会使电流在绝缘块体的边缘流动。一个尚未通过实验验证的关键预测是，在时间反演对称性破缺的情况下边缘传导会失效。在此，我们首先为静电门控量子自旋霍尔器件的磁场依赖性建立了一个系统框架。然后，我们使用微波阻抗显微镜研究了时间反演对称性破缺情况下倒置量子阱器件的边缘传导，并将我们的研究结果与非倒置器件进行了比较。在零磁场下，只有倒置器件在其局部电导率分布中显示出清晰的边缘传导，这与理论相符。令人惊讶的是，边缘传导在高达9 T的磁场下仍然存在且变化很小。这表明存在超出简单量子自旋霍尔模型的物理现象，包括材料特定性质以及可能的多体效应。
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