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學術報告    Quantum phase transitions in magnetic topological insulators


【報告題目】 Quantum phase transitions in magnetic topological insulators
【報 告 人】 王亞愚 教授
              清華大學物理系
【時 間】 2019-06-12     4:00 pm (Wedensday)
【地 點】 理工樓801報告廳

【報告摘要】

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.

																										

【報告人簡介】
																										王亞愚, 1998年本科畢業于中國科技大學物理系,2004年在美國普林斯頓大學物理系獲得博士學位,2004年至2007年在美國加州大學伯克利分校物理系做博士后研究。200712月加入清華大學物理系任教授。主要研究方向為低維量子體系的輸運性質和高溫超導體的掃描隧道顯微學研究。曾獲Miller Fellowship Award (2004)William McMillan Award (2006)、美國李氏基金會杰出成就獎(2008)、國家自然科學基金委杰出青年科學基金(2009)、中國科協青年科技獎(2013)、低溫物理學會馬丁-伍德爵士中國獎(2013)、中國物理學會黃昆物理獎(2015)、“萬人計劃”創新領軍人才(2016)、2018年國家自然科學一等獎(第二完成人)。
 
																										
																										

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