Coherence properties of a 2D trapped Bose gas around the superfluid   transition
  We measure the momentum distribution of a 2D trapped Bose gas and observe the increase of the range of coherence around the Berezinskii-Kosterlitz-Thouless (BKT) transition. We quantitatively compare our observed profiles to both a Hartee-Fock mean-field theory and to quantum Monte-Carlo simulations. In the normal phase, we already observe a sharpening of the momentum distribution. This behavior is partially captured in a mean-field approach, in contrast to the physics of the BKT transition. 
T. Plisson (LCFIO), B. Allard (LCFIO), M. Holzmann (LPTMC, LPMMC), G.   Salomon (LCFIO), Alain Aspect (LCFIO), Philippe Bouy...
physics.atom-ph