Doping driven metal-insulator transitions and charge orderings in the   extended Hubbard model
  We perform a thorough study of an extended Hubbard model featuring local and nearest-neighbor Coulomb repulsion. Using dynamical mean-field theory we investigated the zero temperature phase-diagram of this model as a function of the chemical doping. The interplay between local and non-local interaction drives a variety of phase-transitions connecting two distinct charge-ordered insulators, i.e., half-filled and quarter-filled, a charge-ordered metal and a Mott insulating phase. We characterize these transitions and the relative stability of the solutions and we show that the two interactions conspire to stabilize the quarter-filled charge ordered phase. 
K. J. Kapcia, S. Robaszkiewicz, M. Capone, and A. Amaricci
cond-mat.str-el cond-mat.mtrl-sci cond-mat.quant-gas cond-mat.stat-mech physics.comp-ph