Population and Phase Coherence during the Growth of an Elongated Bose-Einstein Condensate

TL;DR

This paper investigates the growth dynamics of an elongated Bose-Einstein condensate, highlighting the impact of phase fluctuations on growth rate and coherence development through experiments and simulations.

Contribution

It introduces a model linking phase fluctuations to reduced bosonic stimulation, improving understanding of condensate growth in elongated traps.

Findings

Phase fluctuations cause a delay in condensate growth.

Phase coherence evolves over time as measured by Bragg spectroscopy.

A simple model explains the reduction in growth rate due to phase fluctuations.

Abstract

We study the growth of an elongated phase-fluctuating condensate from a non-equilibrium thermal cloud obtained by shock-cooling. We compare the growth of the condensate with numerical simulations, revealing a time delay and a reduction in the growth rate which we attribute to phase fluctuations. We measure the phase coherence using momentum Bragg spectroscopy, and thereby observe the evolution of the phase coherence as a function of time. Combining the phase coherence results with the numerical simulations, we suggest a simple model for the reduction of the growth rate based on the reduction of bosonic stimulation due to phase fluctuations and obtain improved agreement between theory and experiment.