报告题目：Quantum anomalous Hall effect in magnetic topological insulators

主讲嘉宾：何珂副教授（清华大学）

          State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics

时   间：10月23日（周五）下午14:00

地    点：师昌绪楼 403 会议室

报告简介：

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 QAH insulator can be realized in a ferromagnetic topological insulator (TI) film as the result of magnetically induced gap-opening at the Dirac surface states. With molecular beam epitaxy techniques, we have prepared thin films of magnetically doped (Bi,Sb)2Te3 TI with well-controlled composition, thickness and chemical potential, and obtained ferromagnetic insulator phase in them. In such magnetic TI films, we have experimentally observed the quantization of the Hall resistance at h/e2 at zero field, accompanied by a considerable reduction in the dissipation of electron transport, which unambiguously demonstrate the occurrence of the QAH effect. The temperature, thickness and magnetic-doping-level dependences of the QAH effect have been systematically studied, which clarifies the roles of the band structure, electron localization and magnetic order in the effect and provides clues for obtaining the effect at a higher temperature. The experimental progresses in the QAH effect pave the ways for applications of dissipationless quantum Hall edge states in low-energy-consuming devices and for realizations of other novel quantum phenomena such as chiral topological superconductivity and axion electrodynamics.

报告人简介：

Dr. Ke He received his bachelor degree from Department of Physics, Shandong University in 2000 and 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 in Department of Physics, Tsinghua University. The main research interests of Dr. Ke He in recent years are molecular beam epitaxy growth and characterizations of thin films of various topological materials and studies on the topological quantum phenomena in them.

欢迎所内职工和研究生前来交流！