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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. A fundamental question concerning the QAH effect is whether it is merely a zero-magnetic-field quantum Hall effect, or if it can host unique quantum phases that are unavailable elsewhere. There are two features that distinguish the magnetic TIs from other quantum Hall systems, namely the strong disorders caused by magnetic dopants and existence of magnetic domains. Because disorder and magnetism play pivotal roles in the phase diagram of two-dimensional electron systems, accurate manipulation of them may create exotic QAH-based phases and quantum critical phenomena.  

        In this talk we report transport studies on a series of QAH samples with different type and density of magnetic dopants. We find strong evidence for the existence of two novel quantum phases: the QAH liquid and anomalous Hall insulator. For the anomalous Hall insulator, external magnetic field drives it into the QAH liquid state via a quantum critical point, but the critical behavior deviates significantly from that in conventional quantum Hall effect. We propose that the transmission between chiral edge states, tunable by disorder and magnetic domain structure, is the key for unraveling the peculiar quantum transport phenomena in magnetic TIs. We will also present recent observations of the axion insulator to Chern insulator quantum phase transition in the newly discovered antiferromagnetic TI MnBi2Te4.

																										

																											王亚愚， 1998年本科毕业于中国科技大学物理系，2004年在美国普林斯顿大学物理系获得博士学位，2004年至2007年在美国加州大学伯克利分校物理系做博士后研究。2007年12月加入清华大学物理系任教授。主要研究方向为低维量子体系的输运性质和高温超导体的扫描隧道显微学研究。曾获Miller Fellowship Award (2004)、William McMillan Award (2006)、美国李氏基金会杰出成就奖（2008）、国家自然科学基金委杰出青年科学基金（2009）、中国科协青年科技奖（2013）、低温物理学会马丁-伍德爵士中国奖（2013）、中国物理学会黄昆物理奖（2015）、“万人计划”创新领军人才（2016）、2018年国家自然科学一等奖（第二完成人）