Density modulations in an elongated Bose-Einstein condensate released from a disordered potential

TL;DR

This paper investigates how weak disorder causes large density modulations in elongated Bose-Einstein condensates during time-of-flight expansion, distinguishing their origin from phase fluctuations through experiments and theoretical analysis.

Contribution

It demonstrates that density modulations arise from initial density variations caused by disorder, not from phase fluctuations, supported by numerical and analytical models.

Findings

Density modulations depend on disorder strength

Modulations originate from initial density variations

Phase fluctuations are not the primary cause

Abstract

We observe large density modulations in time-of-flight images of elongated Bose-Einstein condensates, initially confined in a harmonic trap and in the presence of weak disorder. The development of these modulations during the time-of-flight and their dependence with the disorder are investigated. We render an account of this effect using numerical and analytical calculations. We conclude that the observed large density modulations originate from the weak initial density modulations induced by the disorder, and not from initial phase fluctuations (thermal or quantum).