Expansion of a Bose-Einstein Condensate in the Presence of Disorder

TL;DR

This paper investigates how disorder affects the expansion of a Bose-Einstein condensate, revealing that interactions can promote diffusion and counteract localization caused by randomness.

Contribution

It introduces a parameter controlling BEC expansion in disordered potentials and demonstrates the role of interactions in facilitating diffusive spreading.

Findings

Interactions promote diffusive expansion of BEC.

Disorder can localize the condensate without interactions.

A single parameter governs the expansion dynamics.

Abstract

Expansion of a Bose-Einstein condensate (BEC) is studied, in the presence of a random potential. The expansion is controlled by a single parameter, $(\mu\tau_{eff} /\hbar)$, where $\mu$ is the chemical potential, prior to the release of the BEC from the trap, and $\tau_{eff}$ is a transport relaxation time which characterizes the strength of the disorder. Repulsive interactions (nonlinearity) facilitate transport and can lead to diffusive spreading of the condensate which, in the absence of interactions, would have remained localized in the vicinity of its initial location.