Wang Shu-Wei, Xiao Di, Dou Ziwei, Cao Moda, Zhao Yi-Fan, Samarth Nitin, Chang Cui-Zu, Connolly Malcolm R, Smith Charles G
Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Phys Rev Lett. 2020 Sep 18;125(12):126801. doi: 10.1103/PhysRevLett.125.126801.
Doping a topological insulator (TI) film with transition metal ions can break its time-reversal symmetry and lead to the realization of the quantum anomalous Hall (QAH) effect. Prior studies have shown that the longitudinal resistance of the QAH samples usually does not vanish when the Hall resistance shows a good quantization. This has been interpreted as a result of the presence of possible dissipative conducting channels in magnetic TI samples. By studying the temperature- and magnetic-field-dependence of the magnetoresistance of a magnetic TI sandwich heterostructure device, we demonstrate that the predominant dissipation mechanism in thick QAH insulators can switch between nonchiral edge states and residual bulk states in different magnetic-field regimes. The interactions between bulk states, chiral edge states, and nonchiral edge states are also investigated. Our Letter provides a way to distinguish between the dissipation arising from the residual bulk states and nonchiral edge states, which is crucial for achieving true dissipationless transport in QAH insulators and for providing deeper insights into QAH-related phenomena.
用过渡金属离子对拓扑绝缘体（TI）薄膜进行掺杂可以打破其时间反演对称性，并导致量子反常霍尔（QAH）效应的实现。先前的研究表明，当霍尔电阻呈现良好的量子化时，QAH样品的纵向电阻通常不会消失。这被解释为磁性TI样品中可能存在耗散传导通道的结果。通过研究磁性TI三明治异质结构器件磁电阻的温度和磁场依赖性，我们证明了厚QAH绝缘体中的主要耗散机制可以在不同磁场区域的非手性边缘态和残余体态之间切换。我们还研究了体态、手性边缘态和非手性边缘态之间的相互作用。我们的论文提供了一种区分残余体态和非手性边缘态产生的耗散的方法，这对于在QAH绝缘体中实现真正的无耗散输运以及深入了解与QAH相关的现象至关重要。
