Slow Thermalization Between a Lattice and Free Bose Gas

TL;DR

This study investigates how a lattice-bound Bose gas and a free Bose gas exchange energy, revealing suppressed thermalization due to dispersion mismatch, which impacts cooling strategies for strongly correlated lattice gases.

Contribution

It demonstrates experimentally that dispersion mismatch suppresses thermalization between lattice-bound and free Bose gases, confirmed by theoretical predictions.

Findings

Suppressed energy exchange observed between the gases.

Dispersion mismatch reduces phase space for collisions.

Implications for cooling strongly correlated gases.

Abstract

Using a 3D spin-dependent optical lattice, we study thermalization and energy exchange between two ultracold Bose gases, one of which is bound to the lattice and another that is free from the lattice potential. Disruption of inter-species thermalization is revealed through measurements of condensate fraction after the lattice is superimposed on the parabolic confining potential. By selectively heating the lattice-bound species and measuring the rate of heat transfer to the free state, suppression of energy exchange is observed. Comparison with a Fermi's golden rule prediction confirms that this effect is caused by a dispersion mismatch that reduces the phase space available for elastic collisions. This result has critical implications for methods proposed to cool strongly correlated lattice gases.