banner8 banner8_m

News and Events

PAST EVENTS

BACK
Seminars

CTCP Seminar: Anomaly pattern of point groups and high-order topological states

Speaker Prof. Yang QI
Affiliation Fudan University
Date October 30, 2024 (Wednesday)
Time 4:00 p.m.
Venue KKLG101, LG1/F, K.K. Leung Building, Main Campus, The University of Hong Kong

Abstract

An essential feature of topological crystalline states (TCSs), which are short-range-entanged topological states protected by crystalline symmetries, is they generally have high-order gapless boundary states, such as one-dimensional hinge states and zero-dimensional corner states on a two-dimensional surface. Therefore, such TCSs are also called high-order topological states. In this work, we design a systematic method to compute possible high-order boundary states of a TCS for all possible surface geometries. We show that the location of surface gapless region, dubbed the anomaly pattern, can be symmetrically and continuously deformed without changing the topologically-protected gapless states, and such deformation defines a homotopy equivalence between anomaly patterns. The list of equivalent classes of anomaly patterns are completely determined by the point-group symmetry, and it is universal for all types of TCSs, including bosonic, free-fermion and interacting-fermion states. We also describe how to compute the anomaly pattern of a bulk topological state, for all types of TCSs.
 

This event is jointly organized by the Department of Physics and HK Quantum Institute of Science & Technology.

 

Anyone interested is welcome to attend.