Fast thermalization and Helmholtz oscillations of an ultracold Bose gas

TL;DR

This paper theoretically investigates the transport dynamics of an ultracold Bose gas, revealing fast thermalization and the potential observation of Helmholtz oscillations at finite temperatures, with implications for understanding superfluid and normal component interactions.

Contribution

It introduces a combined hydrodynamic and Landauer-Buttiker formalism to model transport in ultracold Bose gases, predicting observable plasma oscillations and rapid thermalization effects.

Findings

Helmholtz oscillations can be observed at non-zero temperatures below Tc.

Ultracold Bose gases exhibit fast thermalization due to high compressibility.

Comparison shows differences in thermalization between Bose gases and ideal fermionic gases.

Abstract

We analyze theoretically the transport properties of a weakly-interacting ultracold Bose gas enclosed in two reservoirs connected by a constriction. We assume that the transport of the superfluid part is hydrodynamic, and we describe the ballistic transport of the normal part using the Landauer-Buttiker formalism. Modeling the coupled evolution of the phase, atom number, and temperature mismatches between the reservoirs, we predict that Helmholtz (plasma) oscillations, induced by an initial imbalance in atom numbers, can be observed at non-zero temperatures below Tc. We show that, because of its strong compressibility, the ultracold Bose gas is characterized by a fast thermalization compared to the damping time for plasma oscillations, accompanied by a fast transfer of the normal component through the constriction. This fast thermalization also affects the gas above Tc, where we present an explicit comparison to the ideal fermionic case.