Visibility of ultra-cold Bose system in triangular optical lattices
  In this paper, by treating the hopping parameter in Bose-Hubbard model as a perturbation, with the help of the re-summed Green's function method and cumulants expansion, the momentum distribution function of the ultra-cold Bose system in triangular optical lattice is calculated analytically. By utilizing it, the time-of-flight absorption picture is plotted and the corresponding visibility is determined. The comparison between our analytical results and the experimental data from Ref.[4] exhibits a qualitative agreement. 
Zhi Lin, Jun Zhang, and Ying Jiang
cond-mat.quant-gas cond-mat.stat-mech