# Can a photonic thermalization gap arise in disordered non-Hermitian Hamiltonian systems?

## TL;DR

This paper investigates whether a thermalization gap, protected by chiral symmetry in Hermitian photonic systems, can also occur in non-Hermitian systems, finding it generally does not and thermalization increases with disorder.

## Contribution

It demonstrates that the chiral-symmetry protected thermalization gap does not occur in non-Hermitian photonic systems, contrasting with Hermitian cases and clarifying the role of non-Hermitian effects.

## Key findings

- Thermalization gap disappears in non-Hermitian systems.
- Degree of thermalization increases with disorder strength.
- Thermalization gap may only be observed in highly controlled experiments.

## Abstract

The phenomenon of chiral-symmetry protected thermalization gap in Hermitian photonic systems is counterintuitive as it implies that the photon coherence can be continuously improved by disorders towards an asymptotic limit. We show that the phenomenon disappears in time-independent, non-Hermitian photonic systems even when the chiral symmetry is well preserved. In fact, the degree of thermalization generally increases with the disorder strength, in agreement with intuition. As non-Hermitian characteristics (e.g., weak gain and loss) can be expected in realistic physical situations, the phenomenon of thermalization gap may be observed but only in well controlled experiments with high quality materials.