Phase-fluctuating 3D condensates in elongated traps

D. S. Petrov, G. V. Shlyapnikov, J. T. M. Walraven

Published 2001-04-19, updated 2001-04-26Version 2

We find that in very elongated 3D trapped Bose gases, even at temperatures far below the BEC transition temperature Tc, the equilibrium state will be a 3D condensate with fluctuating phase (quasicondensate). At sufficiently low temperatures the phase fluctuations are suppressed and the quasicondensate turns into a true condensate. The presence of the phase fluctuations allows for extending thermometry of Bose-condensed gases well below those established in current experiments.