Momentum Spectroscopy of Phase Fluctuations of an Elongated Bose-Einstein Condensate

TL;DR

This study measures the momentum distribution of an elongated Bose-Einstein condensate at various temperatures, confirming theoretical predictions about phase fluctuations and coherence length in a quasicondensate.

Contribution

It provides experimental validation of phase fluctuation behavior and coherence properties in elongated BECs, with high aspect ratio measurements.

Findings

Coherence length is significantly smaller than condensate length.

Momentum spectrum has a Lorentzian shape indicating phase fluctuations.

Results agree quantitatively with theoretical models.

Abstract

We have measured the momentum distribution of an elongated BEC (aspect ratio of 152), for temperatures below the critical temperature. The corresponding coherence length is significantly smaller than the condensate length in a wide range of temperature, in quantitative agreement with theoretical predictions. The Lorentzian shape of the momentum spectrum supports the image of a phase fluctuating quasicondensate.