The critical temperature of a trapped, weakly interacting Bose gas

TL;DR

This paper measures the critical temperature of a trapped weakly interacting Bose gas, confirming mean-field theory predictions and observing hydrodynamic effects, while ruling out ideal-gas behavior and critical fluctuation shifts.

Contribution

It provides precise experimental data on the critical temperature dependence and introduces a thermometry method accounting for hydrodynamic expansion effects.

Findings

Critical temperature deviates from ideal-gas predictions.

Results agree with mean-field theory.

Hydrodynamic expansion observed in thermal component.

Abstract

We report on measurements of the critical temperature of a harmonically trapped, weakly interacting Bose gas as a function of atom number. Our results exclude ideal-gas behavior by more than two standard deviations, and agree quantitatively with mean-field theory. At our level of sensitivity, we find no additional shift due to critical fluctuations. In the course of this measurement, the onset of hydrodynamic expansion in the thermal component has been observed. Our thermometry method takes this feature into account.