Bose Einstein condensation and superfluidity in an open system: theory

TL;DR

This paper introduces a new theoretical framework for describing Bose-Einstein condensation and superfluidity in open systems with finite particle lifetime, highlighting the emergence of superfluid characteristics under non-equilibrium conditions.

Contribution

It develops a formalism for weakly interacting bosons with finite lifetime interacting with a thermal bath, extending the understanding of superfluidity beyond equilibrium.

Findings

Elementary excitations exhibit a linear spectrum indicative of superfluidity.

The sound velocity in the condensate is renormalized compared to equilibrium.

Superfluid features can emerge in non-equilibrium open systems.

Abstract

We propose a new theoretical formalism which describes the Bose Einstein condensation of weakly interacting bosons with finite life time interacting with a thermal bath. We show that if a quasi-thermal distribution function of particles is achieved, the elementary excitations of the condensate show a linear spectrum characteristic of a superfluid, with a renormalized sound velocity with respect to the equilibrium case.