Reversible Formation of a Bose-Einstein Condensate

TL;DR

This paper demonstrates a reversible method to increase phase-space density in ultracold sodium gases, enabling the transition to Bose-Einstein condensation and revealing interaction effects on condensate fraction.

Contribution

It introduces a novel adiabatic technique combining magnetic and optical forces to reversibly induce Bose-Einstein condensation in ultracold gases.

Findings

Phase-space density increased by up to 50-fold

Achieved condensate fractions up to 30%

Observed reduction in condensate fraction due to interactions

Abstract

We present a method of adiabatically changing the local phase-space density of an ultracold gas, using a combination of magnetic and optical forces. Applying this method, we observe phase-space density increases in a gas of sodium atoms by as much as 50-fold. The transition to Bose-Einstein condensation was crossed reversibly, attaining condensate fractions of up to 30%. Measurements of the condensate fraction reveal its reduction due to interactions.