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

TL;DR

This paper investigates the two-band Hubbard model and finds that strong electron correlations can lead to phase separation into regions with different charge densities, especially when bandwidth ratios are large.

Contribution

It introduces the analysis of phase separation in a two-band model under strong Coulomb repulsion, highlighting the conditions favoring inhomogeneity.

Findings

Phase separation occurs without magnetic order.

Large bandwidth ratios enhance phase separation.

Inhomogeneity size is estimated considering surface and electrostatic energies.

Abstract

The two-band Hubbard model is used to analyze a possibility of a non-uniform 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 separation 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.