Reaching the hydrodynamic regime in a Bose-Einstein condensate by suppression of avalanche

TL;DR

This paper demonstrates achieving a hydrodynamic Bose-Einstein condensate by low-density evaporative cooling that suppresses avalanches, allowing control over collisional properties and observing hydrodynamic behavior through heating measurements.

Contribution

It presents a method to reach the hydrodynamic regime in BECs by suppressing avalanches during cooling, enabling new studies of collisional dynamics.

Findings

Produced a BEC with 120 million atoms.

Tuned collisional opacity from collisionless to hydrodynamic regime.

Observed heating indicative of hydrodynamic behavior.

Abstract

We report the realization of a Bose-Einstein condensate (BEC) in the hydrodynamic regime. The hydrodynamic regime is reached by evaporative cooling at a relative low density suppressing the effect of avalanches. With the suppression of avalanches a BEC containing 120.10^6 atoms is produced. The collisional opacity can be tuned from the collisionless regime to a collisional opacity of more than 3 by compressing the trap after condensation. In the collisional opaque regime a significant heating of the cloud at time scales shorter than half of the radial trap period is measured. This is direct proof that the BEC is hydrodynamic.