Superfluid Stiffness of a Driven Dissipative Condensate with Disorder

TL;DR

This paper investigates whether driven quantum condensates exhibit superfluidity in the presence of disorder, finding that in dimensions less than four, superfluid stiffness vanishes beyond a critical size, indicating non-superfluid behavior in large systems.

Contribution

It provides a theoretical analysis of superfluidity in driven, disordered condensates, especially highlighting the size-dependent transition in two-dimensional systems.

Findings

Superfluid stiffness vanishes for large condensates in dimensions d<4.

Superfluid behavior persists only in small systems, not in the thermodynamic limit.

Non-equilibrium condensates are generally not superfluid in large, disordered systems.

Abstract

Observations of macroscopic quantum coherence in driven systems, e.g. polariton condensates, have strongly stimulated experimental as well as theoretical efforts during the last decade. We address the question of whether a driven quantum condensate is a superfluid, allowing for the effects of disorder and its non-equilibrium nature. We predict that for spatial dimensions d<4 the superfluid stiffness vanishes once the condensate exceeds a critical size, and treat in detail the case d=2. Thus a non-equilibrium condensate is not a superfluid in the thermodynamic limit, even for weak disorder, although superfluid behavior would persist in small systems.