Chiral metals and entrapped insulators in a one-dimensional topological non-Hermitian system

TL;DR

This paper explores non-Hermitian topological phases in a one-dimensional fermionic system, revealing distinct non-equilibrium steady states with unique transport, entanglement, and boundary properties.

Contribution

It introduces a comprehensive analysis of many-body steady states in a non-Hermitian extension of the SSH model, highlighting new phases and topological features.

Findings

Identification of non-equilibrium phases with finite currents or particle entrapment

Discovery of topological boundary modes in steady states

Analysis of entanglement and correlation properties in different phases

Abstract

In this work we study many-body 'steady states' that arise in the non-Hermitian generalisation of the non-interacting Su-Schrieffer-Heeger model at a finite density of fermions. We find that the hitherto known phase diagrams for this system, derived from the single-particle gap closings, in fact correspond to distinct non-equilibrium phases, which either carry finite currents or are dynamical insulators where particles are entrapped. Each of these have distinct quasi-particle excitations and steady state correlations and entanglement properties. Looking at finite-sized systems, we further modulate the boundary to uncover the topological features in such steady states -- in particular the emergence of leaky boundary modes. Using a variety of analytical and numerical methods we develop a theoretical understanding of the various phases and their transitions, and uncover the rich interplay of non-equilibrium many-body physics, quantum entanglement and topology in a simple looking, yet a rich model system.