Exploring exotic topological phases

主 讲 人 ：汪子丹    教授

活动时间：03月08日10时45分    

地      点 ：理科群2号楼A408

讲座内容：

Symmetry plays a key role in exploring many topological phases. In this talk, non-Hermitian spatial symmetries, a class of symmetries that have no counterparts in Hermitian systems, and how normal and exceptional topological semimetals can be stabilized by these symmetries will be will be introduced. Different from internal ones, spatial symmetries act nonlocally in momentum space and enforce global constraints on both band degeneracies and topological quantities at different locations. Notably, the nonlocal Hermitian conjugate pair of exceptional or normal band degeneracies may be enforced by non-Hermitian spatial symmetries. Remarkably, it is found that these pairs lead to the symmetry-enforced violation of the Fermion doubling theorem in the long-time limit.  On the other hand, for time-reversal and sublattice symmetries, there are six ramified symmetry classes leading to novel topological classifications with various non-Hermitian skin effects. As artificial crystals are the main experimental platforms for non-Hermitian physics, there exists the symmetry barrier for realizing topological physics in the six ramified symmetry classes. Here we present a general mechanism to cross the symmetry barrier, suggesting that gauge structures may significantly enrich non-Hermitian physics at the fundamental level.

主讲人介绍：

汪子丹，香港大学物理系讲座教授，兼香港量子研究院院长。曾获国家自然科学奖二等奖等多项国家和省部级科技奖励，并入选教育部长江学者讲座教授、国家基金委海外杰青等人才项目。长期从事量子物理和凝聚态物理的理论研究，在量子几何相位、量子计算、拓扑物理等前沿领域做出了一系列创新性研究成果。

发布时间：2024-03-07 08:49:56