# Excitonic skin effect

## TL;DR

This paper introduces the excitonic skin effect, a boundary localization phenomenon for particle-hole pairs caused by strong interactions and imaginary vector potentials, with implications for non-Hermitian physics.

## Contribution

It presents a novel boundary localization effect for excitons in non-Hermitian systems, linking strong interactions, imaginary vector potentials, and boundary phenomena.

## Key findings

- Boundary localization of particle-hole pairs due to imaginary vector potentials
- Exponential growth of pairing effects in a non-Hermitian bosonic Kitaev model
- Potential for experimental realization in atomic and electronic systems

## Abstract

We show that strong interactions combined with band-dependent imaginary vector potentials give rise to boundary localization of particle-hole pairs, which we term the excitonic skin effect. In a bilayer system with layer-specific gain/loss and an in-plane magnetic field, excitons experience a net imaginary vector potential, resulting in directional amplification of particle-hole pairs. Including nearest-neighbor interactions leads to a non-Hermitian bosonic Kitaev model, where the pairing effects grow exponentially with the size of the system, revealing a unique form of critical skin effect in interacting systems. Our framework applies to both atomic and electronic platforms and is directly testable in current experiments. These results also provide a route to explore non-Hermitian analogs of tensor gauge fields.