Fast Thermalization and Helmholtz Oscillations of an Ultracold Bose Gas

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 can be observed at nonzero temperatures below T-c. We show that, because of its strong compressibility, the 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. This fast thermalization also affects the gas above T-c, where we present a comparison to the ideal fermionic case. Moreover, we outline the possible realization of a superleak through the inclusion of a disordered potential.