Charge ordering and phase separation in the infinite dimensional extended Hubbard model

TL;DR

This study investigates the extended Hubbard model in infinite dimensions, revealing charge ordering, phase separation, and reentrant transitions influenced by Coulomb interactions, with implications for doped manganites.

Contribution

It provides a detailed phase diagram of the extended Hubbard model using dynamical mean field theory, highlighting charge order and phase separation phenomena.

Findings

Charge order persists at finite temperature around half-filling.

Phase separation occurs between charge-ordered and disordered phases at low temperatures.

Reentrant charge-ordering transition observed in certain doping regimes.

Abstract

We study the extended Hubbard model with both on-site (U) and nearest neighbor (V) Coulomb repulsion using the exact diagonalization method within the dynamical mean field theory. For a fixed U (U=2.0), the T-n phase-diagrams are obtained for V=1.4 and V=1.2, at which the ground states of n=1/2 system is charge-ordered and charge-disordered, respectively. In both cases, robust charge order is found at finite temperature and in an extended filling regime around n=1/2. The order parameter changes non-monotonously with temperature. For V=1.4, phase separation between charge-ordered and charge-disordered phases is observed in the low temperature and n < 0.5 regime. It is described by an "S"-shaped structure of the n-/mu curve. For V=1.2, the ground state is charge-disordered, and a reentrant charge-ordering transition is observed for 0.42 < n < 0.68. Relevance of our results to experiments for doped manganites is discussed.