摘要

Axion was postulated as an elementary particle with a low mass and weak interaction in particle physics to solve the strong CP (charge conjugation and parity) puzzle, and later axion was also considered to be a possible component of dark matter in the universe. However, the existence of axions in nature has not been confirmed. Interestingly, axions arise out of pseudoscalar fields derived from the Chern-Simons theory in condensed matter physics. In antiferromagnetic insulators, the axion field can become dynamical due to spin-wave excitations and exhibits rich exotic phenomena, such as the chiral magnetic effect and axion polariton. However, antiferromagnetic dynamical axion insulator has yet been experimentally identified in realistic materi- als. Very recently, MnBi2Te4 was discovered to be an antiferromagnetic topological insulator with a quantized static axion field protected by inversion symmetry P and magnetic-crystalline symmetry S. In this talk, we will show that both the P and S symmetries in MnBi2Te4 films are spontaneously broken and that substantially enhanced dynamical magnetoelectric effects could be realized through tuning the film thickness, temperature or element substitutions. Our results show that antiferromagnetic topological insulator films of MnBi2Te4 and related compounds could provide a promising material platform to experimentally study axion electrodynamics.

Referee:

arxiv 2010.05424 (2020)

arxiv 2011.04916 (2020)

PRL 122, 206401 (2019)

PRB 101, 081109 (R) (2020)

CPL (express) 37, 077304 (2020)

报告人简介

2000-2004年，在中国科学技术大学学习，获得理学学士学位；
2004-2009年，在中国科学院物理研究所学习，获得理学博士学位；
2010-2015年，在美国斯坦福大学从事博士后研究工作；
2015年至今，被聘为南京大学物理学院教授。

目前是南京大学物理学院和固体微结构物理国家重点实验室教授，博士生导师。主要研究兴趣是，结合第一性原理方法、紧束缚近似方法和kp模型方法等理论方法，探索和理解凝聚态物理中的新奇物性，特别是凝聚态物理中的各种拓扑物质态。

主要荣誉：

2011年，获得香港 ‘求是杰出科技成就奖集体奖’。

2015年，入选“国家海外高层次人才引进计划”（青年项目）。

2018年，获得教育部霍英东青年教师基金资助。

2020年，获得江苏省杰出青年基金资助。