Metal-Insulator transition in optical lattice system with site-dependent   interactions
  We investigate the half-filled Hubbard model with spatially alternating interactions by means of the two-site dynamical mean-field theory. It is found that a single Mott transition occurs when two kinds of interactions are increased. This implies that the different interactions are essentially irrelevant at the critical point. The nature of the Mott states is also addressed. 
Takamitsu Saitou, Akihisa Koga and Atsushi Yamamoto
cond-mat.str-el