报告题目: Symmetry Invariants of Quasiparticles in Magnetic Semimetals

报 告 人: 刘正鑫 教授（中国人民大学）

邀 请 人: 杨丽平

时    间: 10:00 AM , 2023.5.22

地    点: bat365官网登录入口LE201

Abstract : It is known that particles carry presentations (Reps) of their symmetry groups, and different quasi-particles are distinguished by their different quantum numbers. However, it is less known that between the Reps and the symmetry groups there is an extra layer of data called symmetry invariants. Certain invariants of particles which are locked in high energy physics can be unlocked in quasi-particles in condensed matter physics.  Furthermore, there are much more quasiparticles in magnetic materials than in non-magnetic materials. From the k.p theory, we can figure out the physical response of the quasi-particles. Interestingly we find that the electric-magnetic response theory of some quasi-particles respect SO(4) algebra. And a large class of particles in magnetic semimetals can exhibit an exotic cross Larmor precession, and this effect can be observed experimentally from a new phenomena called cross resonant absorption.

Refs: 2009.07864;  2105.12738; PRB 103, 245141 (2021);  JPA 51, 025207 (2018); JPA 54, 265202 (2021)

Brief CV: Prof. Zheng-Xin Liu acquired his Ph.D in the Hong Kong University of Science and Technology in 2010. Then he worked in the Institute for Advanced Study in Tsinghua University and in 2015 he joined Renmin University. His research interest includes quantum magnetism, magnetic semimetals, superconductors, topological order and topological quantum computation. With collaborators, he had worked on the classification of bosonic symmetry protected topological phases and had proposed multi-node quantum spin liquids in spin-orbit coupled magnets.