报告题目：Monopoles in the PT symmetric real band theory

报告人：Dr. Yuxin Zhao (趙宇心)

The University of Hong Kong

报告时间：3月16日 上午10:00

报告地点：新楼5楼多功能厅

报告摘要：

The talk consists of two parts. First, as PT and CP symmetries are fundamental in physics, we talk about the general aspects of the PT or CP invariant topological band theory. We establish a unified topological theory of PT and CP invariant metals and nodal superconductors, based on the mathematically rigorous KO theory. Intriguingly, it is found that the topological charges of Fermi surfaces in the bulk determine an exotic direction-dependent distribution of topological subgap modes on the boundaries. Furthermore, by constructing an exact bulk-boundary correspondence, we show that the topological Fermi points of the PT and CP invariant classes can appear as gapless modes on the boundary of topological insulators with a certain type of anisotropic crystalline symmetry.

Second, we discuss in detail the PT symmetric real Dirac fermions in (3+1) dimensions, which serve as a particularly interesting example in the general theory above. According to the classification above, the specific case has a Z2 classification, and we show that the nontrivial one can be regarded as real monopoles in momentum space serving as a real generalization of complex Weyl fermions, where we call the quasi-particles real Dirac fermions. We construct models of the real Dirac semimetals through revealing connections to recently proposed quantum materials and cold atom experiments about PT symmetric Dirac nodal line semimetals. The real counterparts of topological features of Weyl semimetals, such as Fermi arcs, are investigated in the PT symmetric Dirac semimetals, with underlying reality-dependent topological structures being uncovered.

The talk is mainly based on the publications:

Y. X. Zhao, A. P. Schnyder and Z. D. Wang, Phys. Rev. Lett. 116, 156402 (2016),

Y. X. Zhao and Y. Lu, Phys. Rev. Lett. 118, 056401 (2017).

邀请人：余睿教授