The quantum anomalous Hall (QAH) effect in magnetic topological insulator (TI) represents a new state of matter originated from the interplay between topology and magnetism. The defining characteristics of the QAH ground state are the quantized Hall resistivity (}{$$}}${}${) and vanishing longitudinal resistivity (}{$$}}${}${) in the absence of 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 strong magnetic disorders that induce spatially random magnetization. Because disorder and magnetism play pivotal roles in the phase diagram of two-dimensional electron systems, the 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 of QAH effect can be categorized into two distinct classes: the QAH liquid and anomalous Hall (AH) insulator phases. In the low disorder limit of the QAH liquid regime, we observe a universal quantized longitudinal resistance }{$$}}$_{}${ $=$} h}{/}e}${}^2${ at the coercive field. In the AH insulator regime, we find that a magnetic field can drive it to the QAH liquid phase through a quantum critical point with unique scaling behaviors. We propose that the transmission between chiral edge states at domain boundaries, tunable by disorder and magnetic fields, is the key for determining the QAH ground state.

中文翻译：

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磁异常引起的明显量子异常霍尔基态

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，其起源于拓扑与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（} {$ $}} $ {} $ {）和消失的纵向电阻率（} {$ $}} $ {}$ {）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，还是它可以承载其他地方所没有的独特量子相和相变。QAH系统与其他QH系统最显着的不同之处在于会引起空间随机磁化的强磁异常。由于无序和磁性在二维电子系统的相图中起着关键作用，因此QAH系统中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QAH效应的基态可以分为两类：QAH液体和异常霍尔（AH）绝缘子相。在QAH液体方案的低紊乱极限中，我们观察到了通用的量化纵向阻力} {$$}} $ _ {} $ {$=$} h} {/} e}${}^2${在强制领域。在AH绝缘体体系中，我们发现磁场可以通过具有独特缩放行为的量子临界点将其驱动到QAH液相。我们建议在域边界的手性边缘状态之间的传输，可通过无序和磁场调节，是确定QAH基态的关键。