Finite temperature vortex dynamics in Bose Einstein condensates

We study the decay of vortices in Bose-Einstein condensates at finite temperatures by means of the Zaremba Nikuni Griffin formalism, in which the condensate is modelled by a Gross Pitaevskiiequation, which is coupled to a Boltzmann kinetic equation for the thermal cloud. At finite temperature, an off-centred vortex in a harmonically trapped pancake shaped condensate decays by spiralling out towards the edge of the condensate. This decay, which depends heavily on temperature and atomic collisions, agrees with that predicted by the Hall Vinen phenomenological model of friction force, which is used to describe quantised vorticity in superfluid systems. Our result thus clarifies the microscopic origin of the friction and provides an ab initio determination of its value.