Projective representations and the search for Magnetic Dirac semimetals

by Prof. Zheng-Xin Liu (Department of physics, Renmin University of China)

Friday 19 Jul 2019, 13:30 → 14:30 Asia/Shanghai

Abstract

In the first part of the talk, the eigenfunction method will be applied to

obtain all of the irreducible projective representations (Reps) of finite groups, especially of anti-unitary groups. To this end, we first solve the cocycle equations to obtain the factor system of each class of projective Reps, from which we construct the regular projective Rep and then reduce it into irreducible ones. The second part is focus on the applications of irreducible Reps in condensed matter physics. It will be shown that the spectrum degeneracy induced by irreducible projective Reps may give rise to Dirac cones in Magnetic materials whose symmetry groups are magnetic space groups. We provide the condition for the emergence of Dirac cones on the high symmetrypoints in the Brillouin zone, and enumerate all the type-III and type-IV the magnetic space groups that may host Dirac semimetals.

Biography

Dr. Zheng-Xin Liu obtained his Ph.D in the Hong Kong University of Science and Technology in 2010. After that he worked in the Institute for Advanced Study in Tsinghua University as a post doctor and then as an associate member. He joined Renmin University of China in 2015 as an associate professor. Dr. Liu's research area includes symmetry protected topological phases, quantum magnetism and many-body numerical computations. Recently, his interest is focusing on magnetic systems, including quantum spin liquid (such as Kitaev spin liquid) and magnetic Dirac semimetals.

Division

Particle and Nuclear