题目：Searching for high temperature quantum anomalous Hall systems

报告人：Ke He  Tsinghua University

地点： 教十二-201

时间： 6月9日，周五，15:00-16:00

摘要：

The quantum anomalous Hall (QAH) effect is a quantum Hall effect induced by spontaneous magnetization instead of an external magnetic field. The effect occurs in two-dimensional (2D) insulators with topologically nontrivial electronic band structure characterized by a non-zero Chern number. The experimental observation of the QAH effect in thin films of magnetically doped(Bi,Sb)2Te3 topological insulators (TIs) paves the way for practical applications of dissipationless quantum Hall edge states, but an ultralow temperature of 30 mK is required to reach a perfect quantization. Further studies in this direction require magnetic TI materials that can show the QAH effect at higher temperature. I will introduce the systematic studies on the QAH effect in magnetically doped TI films of different thicknesses, magnetic dopants and compositions in the past years. The results clarify the relationship between the QAH effect and the energy band structure, electronic localization and ferromagnetism of magnetic TI films and provide insights into how to obtain high temperature QAH materials. Recently, by co-doping Cr and V in (Bi,Sb)2Te3TI films, we significantly increase the temperature for the QAH effect to such a level that full quantization is achieved at 300 mK, and zero-field Hall resistance of 0.97 h/e2 is observed at 1.5 K.

个人简介：

Prof. Ke He received his bachelor degree from Department of Physics, Shandong University in 2000and PhD degree from Institute of Physics, Chinese Academy of Sciences in 2006. After working as a postdoctoral researcher in the University of Tokyo for three years, he joined Institute of Physics, Chinese Academy of Sciences in 2009 as an associate professor. From September, 2013, he became an associate professor inDepartment of Physics, Tsinghua University, and became a full professor at 2016. The main research interests of Prof. Ke He in recent years are molecular beam epitaxy growth andcharacterizations of thin filmsof various topological materials and studies on the topological quantum phenomena in them.

欢迎老师和同学参加！