Mesoscopic non-Hermitian skin effect

TL;DR

This paper extends the concept of the non-Hermitian skin effect to finite photonic systems without bulk gain or loss, revealing edge-localized modes linked to topological properties, with implications for lossless photonic structures.

Contribution

It introduces a mesoscopic non-Hermitian skin effect in lossless photonic systems, connecting edge mode localization to point-gap topology in finite-size structures.

Findings

Edge modes can be localized at boundaries despite real spectra under PBC.

The localization is linked to the topological properties of the size-dependent spectrum.

Potential applications include lossless photonic devices like chiral metamaterials.

Abstract

We discuss a generalization of the non-Hermitian skin effect to finite-size photonic structures with neither gain nor loss in the bulk and purely real energy spectrum under periodic boundary conditions (PBC). We show that such systems can still have significant portions of eigenmodes concentrated at the edges and that this edge concentration can be linked to the non-trivial point-gap topology of the size-dependent regularized PBC spectrum, accounting for the radiative losses. As an example, we consider the chiral waveguide quantum electrodynamics platform with an array of atoms coupled to the waveguide. The proposed mesoscopic analogue of the non-Hermitian skin effect could be potentially applied to other seemingly lossless photonic structures, such as chiral resonant all-dielectric metamaterials.