The effect of light assisted collisions on matter wave coherence in   superradiant Bose-Einstein condensates
  We investigate experimentally the effects of light assisted collisions on the coherence between momentum states in Bose-Einstein condensates. The onset of superradiant Rayleigh scattering serves as a sensitive monitor for matter wave coherence. A subtle interplay of binary and collective effects leads to a profound asymmetry between the two sides of the atomic resonance and provides far bigger coherence loss rates for a condensate bathed in blue detuned light than previously estimated. We present a simplified quantitative model containing the essential physics to explain our experimental data and point at a new experimental route to study strongly coupled light matter systems. 
N. S. Kampel, A. Griesmaier, M.P. Hornbak Steenstrup, F. Kaminski, E.   S. Polzik, J. H. M\"uller
cond-mat.quant-gas quant-ph