The bosonic skin effect: boundary condensation in asymmetric transport

TL;DR

This paper investigates a novel boundary condensation phenomenon in asymmetric bosonic transport, revealing a phase transition characterized by boundary-localized Bose condensation and its connection to non-Hermitian topology.

Contribution

It introduces the bosonic skin effect, linking boundary condensation in asymmetric transport to non-Hermitian spectral features and non-equilibrium quantum phases.

Findings

Identification of a boundary-induced Bose-condensed phase

Connection between the skin effect and exceptional points

Potential experimental realizations in cold-atom and photonic systems

Abstract

We study the incoherent transport of bosonic particles through a one dimensional lattice with different left and right hopping rates, as modelled by the asymmetric simple inclusion process (ASIP). Specifically, we show that as the current passing through this system increases, a transition occurs, which is signified by the appearance of a characteristic zigzag pattern in the stationary density profile near the boundary. In this highly unusual transport phase, the local particle distribution alternates on every site between a thermal distribution and a Bose-condensed state with broken U(1)-symmetry. Furthermore, we show that the onset of this phase is closely related to the so-called non-Hermitian skin effect and coincides with an exceptional point in the spectrum of density fluctuations. Therefore, this effect establishes a direct connection between quantum transport, non-equilibrium condensation phenomena and non-Hermitian topology, which can be probed in cold-atom experiments or in systems with long-lived photonic, polaritonic and plasmonic excitations.