Phase separation in a two-band model for strongly correlated electrons

The two-band Hubbard model is used to analyze a possibility of a nonuniform charge distribution in a strongly correlated electron system with two types of charge carriers. It is demonstrated that in the limit of strong on-site Coulomb repulsion, such a system has a tendency to phase separate into the regions with different charge densities even in the absence of magnetic or any other ordering. This tendency is especially pronounced if the ratio of the bandwidths is large enough. The characteristic size of inhomogeneities is estimated, accounting for the surface energy and the electrostatic energy related to the charge imbalance.