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Distinct Quantum Anomalous Hall Ground States Induced by Magnetic Disorders
Physical Review X ( IF 12.5 ) Pub Date : 2020-12-30 , DOI: 10.1103/physrevx.10.041063
Chang Liu , Yunbo Ou , Yang Feng , Gaoyuan Jiang , Weixiong Wu , Shaorui Li , Zijia Cheng , Ke He , Xucun Ma , Qikun Xue , Yayu Wang

The quantum anomalous Hall (QAH) effect in a magnetic topological insulator (TI) represents a new state of matter originating from the interplay between topology and magnetism. The defining characteristics of the QAH ground state are the quantized Hall resistivity (ρyx) and vanishing longitudinal resistivity (ρxx) in the absence of an external magnetic field. A fundamental question concerning the QAH effect is whether it is merely a zero-magnetic-field quantum Hall (QH) effect or if it can host unique quantum phases and phase transitions that are unavailable elsewhere. The most dramatic departure of the QAH systems from other QH systems lies in the magnetic disorders that induce spatially random magnetization. Because disorder and magnetism play pivotal roles in the phase diagram of two-dimensional electron systems, the high degree of magnetic disorders in QAH systems may create novel phases and quantum critical phenomena. In this work, we perform systematic transport studies of a series of magnetic TIs with varied strength of magnetic disorders. We find that the ground state can be categorized into two distinct classes: the QAH phase and the anomalous Hall (AH) insulator phase, as the zero-magnetic-field counterparts of the QH liquid and Hall insulator phases in the QH systems. In the low-disorder limit of the QAH phase, we observe a universal quantized longitudinal resistance ρxx=h/e2 at the coercive field. In the AH insulator regime, we find that a magnetic field can drive it to the QAH phase through a quantum critical point with scaling behaviors that are distinct from those in the QH phase transition. We propose that the transmission between chiral edge states at domain boundaries, tunable by magnetic disorder and magnetic fields, is the key for determining the QAH ground state.

中文翻译:

电磁紊乱引起的独特量子异常霍尔基态

磁拓扑绝缘体(TI)中的量子异常霍尔(QAH)效应代表了一种新的物质状态,该状态源自拓扑和磁性之间的相互作用。QAH基态的定义特征是量化的霍尔电阻率(ρx)和纵向电阻率(ρxx)在没有外部磁场的情况下。关于QAH效应的一个基本问题是,它仅仅是零磁场量子霍尔(QH)效应,还是可以承载其他地方无法获得的独特量子相和相变。QAH系统与其他QH系统最显着的差异在于引起空间随机磁化的磁异常。由于无序和磁性在二维电子系统的相图中起着至关重要的作用,因此QAH系统中高度的磁性无序可能会产生新的相和量子临界现象。在这项工作中,我们对一系列具有不同强度的磁性障碍的磁性TI进行了系统的运输研究。我们发现基态可以分为两类:QAH相和异常霍尔(AH)绝缘子相,作为QH系统中QH液相和霍尔绝缘子相的零磁场对应物。在QAH阶段的无序限度中,我们观察到了通用的量化纵向电阻ρxx=H/Ë2在强制领域。在AH绝缘体状态中,我们发现磁场可以通过量子临界点将其驱动到QAH相,该量子临界点的缩放行为不同于QH相变。我们建议在域边界的手性边缘状态之间的传输,可通过磁场和磁场来调节,是确定QAH基态的关键。
更新日期:2020-12-30
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