Universal routes to spontaneous PT-symmetry breaking in non-hermitian quantum systems

TL;DR

This paper uses random-matrix theory to identify two universal mechanisms for spontaneous PT-symmetry breaking in non-Hermitian quantum systems, with implications for optical experiments and spectral behavior.

Contribution

It reveals two distinct universality classes governing PT-symmetry breaking mechanisms, linking them to different spectral transition behaviors in non-Hermitian systems.

Findings

Spontaneous PT-symmetry breaking occurs via two mechanisms.

Optical experiments align with the orthogonal universality class.

Level crossings can make absorption rates independent of coupling.

Abstract

PT-symmetric systems can have a real spectrum even when their Hamiltonian is non-hermitian, but develop a complex spectrum when the degree of non-hermiticity increases. Here we utilize random-matrix theory to show that this spontaneous PT-symmetry breaking can occur via two distinct mechanisms, whose predominance is associated to different universality classes. Present optical experiments fall into the orthogonal class, where symmetry-induced level crossings render the characteristic absorption rate independent of the coupling strength between the symmetry-related parts of the system.