Edge states at the interface of non-Hermitian systems

TL;DR

This paper explores the existence and properties of topological edge states at interfaces between non-Hermitian insulators, revealing PT symmetry breaking and complex eigenvalues in such states, extending topological concepts beyond Hermitian systems.

Contribution

It introduces the concept of topological edge states in non-Hermitian systems with PT symmetry, demonstrating their emergence with complex energies at interfaces.

Findings

PT symmetry is spontaneously broken at the interface.

Topological edge states with complex energies appear.

Application to a complex SSH model confirms the theory.

Abstract

Topological edge states appear at the interface of topologically distinct two Hermitian insulators. We study the extension of this idea to non-Hermitian systems. We consider PT symmetric and topologically distinct non-Hermitian insulators with real spectra and study topological edge states at the interface of them. We show that PT symmetry is spontaneously broken at the interface during the topological phase transition. Therefore topological edge states with complex energy eigenvalues appear at the interface. We apply our idea to a complex extension of the Su-Schrieffer-Heeger (SSH) model.