Shift of the Bose-Einstein condensation temperature due to dipolar interactions

TL;DR

This study measures how dipolar interactions in ultracold erbium atoms affect the Bose-Einstein condensation temperature, revealing orientation-dependent shifts and aligning with mean-field theory predictions.

Contribution

First experimental observation of BEC critical temperature shift due to dipolar interactions in ultracold erbium atoms with tunable contact interactions.

Findings

Critical temperature depends on dipole orientation.

Results agree with mean-field theoretical predictions.

Paves the way for exploring supersolid and droplet states.

Abstract

We report the first measurements of the BEC critical temperature shift due to dipolar interactions, employing samples of ultracold erbium atoms which feature significant (magnetic) dipole-dipole interactions in addition to tuneable contact interactions. Using a highly prolate harmonic trapping potential, we observe a clear dependence of the critical temperature on the orientation of the dipoles relative to the trap axis. Our results are in good agreement with mean-field theory for a range of contact interaction strengths. This work opens the door for further investigations into beyond-mean-field effects and the finite-temperature phase diagram in the more strongly dipolar regime where supersolid and droplet states emerge.