Eur. Phys. J. B (2022) 95: 97
https://doi.org/10.1140/epjb/s10051-022-00364-3

Regular Article - Solid State and Materials

Clock-symmetric non-Hermitian second-order topological insulator

Department of Applied Physics, University of Tokyo, 7-3-1, 113-8656, Hongo, Japan

^a ezawa@ap.t.u-tokyo.ac.jp

Received: 6 April 2022
Accepted: 10 June 2022
Published online: 21 June 2022

Abstract

We consider a breathing Kagome lattice with complex hoppings by imposing ${\mathbb{Z}}_3$ clock symmetry in the complex-energy plane. It is a non-Hermitian generalization of the second-order topological insulator characterized by the emergence of topological corner states. We construct topological corner states with the ${\mathbb{Z}}_3$ clock-symmetric model. It is also shown that the model is realized in an electric circuit properly designed, where corner states are observed by impedance resonance. We also construct the ${\mathbb{Z}}_4$ and ${\mathbb{Z}}_6$ symmetric models on breathing square and honeycomb lattices, respectively.