Production of smooth flow in racetrack BECs at zero and non--zero temperatures*

We have studied the production of smooth, persistent currents in ultracold (bosonic) gas systems that consist of an atomic BEC and a non-condensate cloud. The BEC is assumed to be strongly confined in a horizontal plane by a vertical harmonic trap and, within this plane, subjected to an arbitrary two-dimensional potential. The racetrack potential is made up of two straight parallel channels connected on both ends by semicircular channels of the same width and energy height as the straightaways. The zero-temperature behavior of the system is simulated using the Gross-Pitaevskii equation and at non-zero temperature by the Zaremba-Nikuni-Griffin model. The flow is realized by stirring along the channel with a rectangular barrier. We conducted simulations of stirring racetrack BECs for a range of different racetrack geometries, barrier speeds and maximum energy heights both at zero and non-zero temperatures. We also investigated the mechanism for producing flow in order to be able to predict the amount of flow and its onset using a 1D model. We will present the results of the simulations and also discuss the effect of temperature on the amount of flow produced.