Effects of Interactions on the Critical Temperature of a Trapped Bose Gas

TL;DR

This study measures how interactions affect the critical temperature of a trapped Bose gas, confirming mean-field predictions for weak interactions and revealing beyond-mean-field effects at stronger interactions.

Contribution

It provides high-precision experimental data on the critical temperature shifts due to interactions, including beyond-mean-field effects in a trapped Bose gas.

Findings

Negative shift of critical temperature for weak interactions

Positive shift indicating beyond-mean-field correlations for strong interactions

Discussion of non-equilibrium effects on critical temperature

Abstract

We perform high-precision measurements of the condensation temperature of a harmonically-trapped atomic Bose gas with widely-tuneable interactions. For weak interactions we observe a negative shift of the critical temperature in excellent agreement with mean-field theory. However for sufficiently strong interactions we clearly observe an additional positive shift, characteristic of beyond-mean-field critical correlations. We also discuss non-equilibrium effects on the apparent critical temperature for both very weak and very strong interactions.