Observing the Formation of Long-range Order during Bose-Einstein Condensation

TL;DR

This paper experimentally observes the real-time formation of long-range order during Bose-Einstein condensation in ultracold atomic gases, revealing how phase coherence develops as the system transitions to a condensed state.

Contribution

It provides direct experimental insights into the dynamics of long-range order formation and phase coherence during Bose-Einstein condensation.

Findings

Growth of spatial coherence observed during condensation

Long-range order forms in real time

Momentum distribution evolves during condensate formation

Abstract

We have experimentally investigated the formation of off-diagonal long-range order in a gas of ultracold atoms. A magnetically trapped atomic cloud prepared in a highly nonequilibrium state thermalizes and thereby crosses the Bose-Einstein condensation phase transition. The evolution of phase coherence between different regions of the sample is constantly monitored and information on the spatial first-order correlation function is obtained. We observe the growth of the spatial coherence and the formation of long-range order in real time and compare it to the growth of the atomic density. Moreover, we study the evolution of the momentum distribution during the nonequilibrium formation of the condensate.