Critical and non critical non-Hermitian topological phase transitions in one dimensional chains

TL;DR

This paper explores non-Hermitian topological phase transitions in a one-dimensional chain model, analyzing edge state behavior, exceptional points, and critical exponents to understand the transition mechanisms.

Contribution

It introduces a detailed analysis of non-Hermitian topological phase transitions using real-space edge states and exceptional point topology, extending understanding beyond Hermitian systems.

Findings

Edge states penetrate into the bulk depending on parameters.

Exceptional points characterize the chiral behavior of edge states.

Critical exponents are determined from edge state penetration lengths.

Abstract

In this work we investigate non-Hermitian topological phase transitions using real-space edge states as a paradigmatic tool. We focus on the simplest non-Hermitian variant of the Su-Schrieffer-Hegger model, including a parameter that denotes the degree of non-hermiticity of the system. We study the behavior of the zero energy edge states at the non-trivial topological phases with integer and semi-integer topological winding number, according to the distance to the critical point. We obtain that depending on the parameters of the model the edge states may penetrate into the bulk, as expected in Hermitian topological phase transitions. We also show that using the topological characterization of the exceptional points, we can describe the intricate chiral behavior of the edge states across the whole phase diagram. Moreover, we characterize the criticality of the model by determining the correlation length critical exponent, directly from numerical calculations of the penetration length of the zero modes edge states.