题目：Intrinsic magnetic topological insulator MnBi2Te4
报告人：徐勇 副教授
清华大学物理系
时间：2019年9月23日（星期一）下午16:00
地点：国家脉冲强磁场科学中心C204
报告摘要：
The interplay of magnetism and topology is a key research subject in condensed matter physics and material science, which offers great opportunities to explore emerging new physics, like the quantum anomalous Hall (QAH) effect, axion electrodynamics and Majorana fermions. However, these exotic physical effects have rarely been realized in experiment, due to the lacking of suitable working materials. In this talk, we will present our recent findings of intrinsic magnetic topological insulators in van der Waals layered MnBi2Te4-family materials [1-6]. The materials intrinsically show two-dimensional (2D) ferromagnetism in the single layer and three-dimensional (3D) A-type antiferromagnetism in the bulk, which could serve as a next-generation material platform for the state-of-art research. We predict extremely rich topological quantum effects with outstanding features in an experimentally available material MnBi2Te4, including a 3D antiferromagnetic topological insulator with the long-sought topological axion states, the type-II magnetic Weyl semimetal (WSM) with one pair of Weyl points, and intrinsic QAH insulators and axion insulators. Recent theoretical and experimental progresses will be introduced. As important progresses, we experimentally observed two exotic topological phases (i.e., axion insulator and Chern insulator) and quantum phase transition between them in one stoichiometric crystal MnBi2Te4 at relatively high temperature [5,6].
参考文献：
[1] J. Li, et al., Intrinsic magnetic topological insulators in van der Waals layered MnBi2Te4-family materials. Sci. Adv. 5, eaaw5685 (2019).
[2] Y. Gong, et al., Experimental realization of an intrinsic magnetic topological insulator. Chin. Phys. Lett. 36, 076801 (2019).
[3] Yang Peng, Yong Xu, Proximity-induced Majorana hinge modes in antiferromagnetic topological insulators. PRB 99, 195431 (2019).
[4] J. Li, et al., Magnetically Controllable Topological Quantum Phase Transitions in Antiferromagnetic Topological Insulator MnBi2Te4. arXiv:1905.00642.
[5] C. Liu, et al., Quantum phase transition from axion insulator to Chern insulator in MnBi2Te4. arXiv:1905.00715.
[6] J. Ge, et al., High-Chern-Number and High-Temperature Quantum Hall Effect without Landau Levels, arXiv: 1907.09947.
报告人简介：
Dr. Yong Xu is now an associate professor at Department of Physics, Tsinghua University (2018-present) and a unit leader of at RIKEN Center for Emergent Matter Science (CEMS) (2015-present). He received his B.S. degree in Physics (2005) and Ph.D. degree in Condensed Matter Physics (2010) at Tsinghua University. Then he worked at Fritz Haber Institute of Max Planck Society (2011-2013) and Stanford University (2013-2015) as a postdoc and a research scholar, respectively. He was awarded the Alexander von Humboldt Fellowship of Germany (2011) and recruited by the National Thousand Young Talents Program of China (2014).
His main research interest is to understand/predict unusual quantum phenomena and novel material properties, based on first-principles calculations.
