Superradiant Raman scattering in an ultracold Bose gas at finite temperature

We study superradiant Raman scattering from an ultracold, but finite, temperature Bose gas in a harmonic trap. Numerical simulations indicate the existence of distinct time scales associated with the decoherence of the condensed versus thermal fractions, and the concomitant preferred scattering from atoms in low-lying trap states in the regime where superradiance takes place on a time scale comparable to an inverse trap frequency. As a consequence the scattered atoms experience a modest reduction in temperature as compared to the unscattered atoms.