Chiral Dissociation of Bound Photon Pairs for a Non-Hermitian Skin Effect

TL;DR

This paper theoretically investigates how bound photon pairs in a chiral waveguide-atom system exhibit edge localization linked to the non-Hermitian skin effect, revealing unique dissociation and localization phenomena.

Contribution

It introduces a novel understanding of bound photon states in chiral waveguide systems, connecting non-Hermitian physics with photon localization and dissociation behaviors.

Findings

Bound photon pairs can localize at the edge of an atomic array.

Infinite lifetime of bound states in infinite arrays contrasts with finite array behavior.

Chiral emission causes asymmetric localization of photon pairs.

Abstract

We theoretically study the bound states of interacting photons propagating in a waveguide chirally coupled to an array of atoms. We demonstrate that the bound photon pairs can concentrate at the edge of the array and link this to the non-Hermitian skin effect. Unlike tight-binding non-Hermitian setups, the bound states in the waveguide-coupled array exhibit infinite radiative lifetimes when the array has an infinite size. However, in a finite array, non-Hermiticity and localization of bound pairs emerge due to their chiral dissociation into scattering states. Counterintuitively, when the photons are preferentially emitted to the right, the bound pairs are localized at the left edge of the array and vice versa.