Phase separation in strongly correlated electron systems with wide and narrow bands: a comparison of the Hubbard-I and DMFT approximations

TL;DR

This paper compares Hubbard-I and DMFT approximations in analyzing phase separation in the Falicov-Kimball model, revealing that phase separation is a fundamental feature in systems with wide and narrow bands.

Contribution

It demonstrates that phase separation occurs in Hubbard-like models with wide and narrow bands, using both Hubbard-I and DMFT approximations, highlighting their similarities at large Coulomb repulsion.

Findings

Both approximations yield similar results at large Coulomb repulsion.

Phase separation is favorable in models with finite bandwidth for heavy electrons.

Phase separation is an inherent feature of systems with wide and narrow bands.

Abstract

The spinless Falicov-Kimball model on the simple cubic lattice is analyzed in the Hubbard-I and dynamical mean field (DMFT) approximations. The Matsubara and real frequency itinerant electron Green's functions, the evolution of the system with doping, and the range of phase separation are found in two approximations. At large values of the on-site Coulomb repulsion both approximations give similar results. The phase separation can be also favorable for a more general model, where heavy electrons have a finite bandwidth. This indicates that the phase separation phenomenon is an inherent feature of the systems described by the Hubbard-like models with wide and narrow bands.