Non-Hermitian Skin Effect from Radiative Coupling in a Reciprocal Chiral Medium

Abstract

We find that long-range radiative coupling through a passive reciprocal chiral medium produces an unusual non-Hermitian skin effect in a chain of electric dipoles. Although the system is reciprocal, the chirality generates polarization-dependent phase accumulation and attenuation, leading to degenerate pairs of skin modes localized at opposite boundaries. We find that the skin mode profile consists of an exponential contribution from an isolated complex-$β$ pole and a longer-range tail proportional to $1/[n(\ln n)^2]$, where $n$ is the distance from the occupied boundary measured in lattice sites. Finite-chain calculations show that part of the OBC spectrum contracts toward the Bloch spectrum, whereas the number of boundary-localized modes remains extensive.