Mean-field dynamics to negative absolute temperatures in the   Bose-Hubbard model
  We apply time-dependent Gutzwiller mean-field theory to provide a qualitative understanding for bosons in optical lattices that approach states corresponding to negative absolute temperatures. We perform the dynamical simulations to relate to the recent experiments by Braun et al. [ S. Braun, J. P. Ronzheimer, M. Schreiber, S. S. Hodgman, T. Rom, I. Bloch and U. Schneider, Science 339 52 (2013)]. Time-of-flight images calculated from the two-dimensional numerical simulations reproduce characteristics of the experimental observations, in particular, the emergence of the four peaks at the corners of the Brillouin zone. 
Akos Rapp
cond-mat.quant-gas