Effective temperature of a superfluid flowing in a random potential

TL;DR

This paper demonstrates that a superfluid flowing in a weak random potential exhibits correlation properties equivalent to a thermal state at an effective temperature, which can be measured experimentally.

Contribution

It introduces the concept of an effective temperature for a superfluid in a disordered potential, linking nonequilibrium correlations to equilibrium thermal behavior.

Findings

Correlation functions match those of a thermal superfluid at an effective temperature

Decay behaviors are exponential in 1D and power-law in 2D

Effective temperature can be measured via interference experiments

Abstract

The spatial fluctuations of a superfluid flowing in a weak random potential are investigated. We employ classical field theory to demonstrate that the disorder-averaged nonequilibrium second-order correlation of the order parameter at zero temperature is identical to the thermally averaged equilibrium counterpart of a uniform superfluid at an effective temperature. The physics behind this equivalence is that scattering of a moving condensate by disorder has the same effect on the correlation function as equilibrium thermal excitations. The correlation function exhibits an exponential decay in one dimension and a power-law decay in two dimensions. We show that the effective temperature can be measured in an interference experiment of ultracold atomic gases.