本学期第五次青年物理教师学术沙龙（午餐报告会）将于下周二11月21日中午举行，由南京大学物理学院赵宇心教授做报告。

报告时间：11月21日 中午12：00

报告地点：南京大学鼓楼校区唐仲英楼B501

报告题目：PT Symmetric Real Topological Insulators and Semimetals

摘要：Spinless fermions, photonic crystals and mechanical systems may have PT symmetry being represented with the relation ( P ^ T^)2 = 1, where P and T stands for spatial inversion and time-reversal, respectively. These PT symmetric systems may be described by essentially real Bloch wave functions forming real band theories due to the anti-unitarity of PT symmetry and the absence of the Kramers degeneracy. In the usual sense, the presence of PT symmetry implies vanishing Chern number, namely there is no PT symmetric Chern insulator and Weyl semimetal. In this talk, I will provide PT symmetric counterparts of Chern insulators and Weyl semimetals in real band theories in a quite dierent sense. The essence is that even for real bands, complex structures can be emerged from equivariant matter which is real representations of symmetry groups, and therefore there may exist monopoles with symmetry-dependent Chern number as their topological charge. The physical consequences of the real topological charge or the real Chern number will be elucidated as well.

报告人简介：南京大学物理学院教授。2010年在北京大学物理系取得学士学位，2014年在香港大学物理系取得博士学位。之后，在德国马普固体物理所和香港大学物理系做博士后和研究助理教授。获得第十三届千人计划青年项目后，于2017年9月回到南京大学物理学院工作。主要从事拓扑半金属和拓扑绝缘体的理论研究，包括：拓扑分类、拓扑不变量的构造、无序下拓扑费米子的非线性sigma模型，等问题。

代表论文：

Y. X. Zhao and Z. D. Wang, Topological classification and stability of Fermi surfaces, Phys. Rev. Lett. 110, 240404 (2013).

Y. X. Zhao and Z. D. Wang, Disordered Weyl semimetals and their topological family, Phys. Rev. Lett. 114, 206602 (2015). 

Y. X. Zhao and Z. D. Wang, Novel Z2 Topological Metals and Semimetals, Phys. Rev. Lett. 116, 016401 (2016).

Y. X. Zhao, A. P. Schnyder, and Z. D. Wang, Unified Theory of PT and CP Invariant Topological Metals and Nodal Superconductors, Phys. Rev. Lett. 116, 156402 (2016).

Y. X. Zhao and Y. Lu, PT Symmetric Real Dirac Fermions and Semimetals, Phys. Rev. Lett. 118, 056401 (2017).

Y. X. Zhao and Z. D. Wang, Topological connection between the stability of Fermi surfaces and topological insulators and superconductors, Phys. Rev. B 89, 075111 (2014).

Y. X. Zhao and A. P. Schnyder, Nonsymmorphic symmetry-required band crossings in topological semimetals, Phys. Rev. B 94, 195109 (2016).

欢迎各位老师参加。

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                       江苏省物理学会青年工作委员会

                                     2017年11月17日