Bose-Einstein condensation into non-equilibrium states studied by condensate focusing

TL;DR

This paper investigates non-equilibrium Bose-Einstein condensates formed through local thermalization, revealing their elongated shape, phase fluctuations, and using condensate focusing to measure phase-coherence length.

Contribution

It introduces condensate focusing as a novel method to measure phase-coherence length in non-equilibrium Bose-Einstein condensates.

Findings

Condensates are longer than equilibrium counterparts with the same atom number.

They exhibit strong phase fluctuations.

Condensate focusing effectively measures phase-coherence length.

Abstract

We report the formation of Bose-Einstein condensates into non-equilibrium states. Our condensates are much longer than equilibrium condensates with the same number of atoms, show strong phase fluctuations, and have a dynamical evolution similar to that of quadrupole shape oscillations of regular condensates. The condensates emerge in elongated traps as the result of local thermalization when the nucleation time is short compared to the axial oscillation time. We introduce condensate focusing as a powerful method to extract the phase-coherence length of Bose-Einstein condensates.