Mesoscopic non-Hermitian skin effect

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.