Charge ordering and correlation effects in the extended Hubbard model

TL;DR

This study uses advanced computational methods to explore how non-local interactions influence phase transitions and electron mobility in the extended Hubbard model on a 2D lattice, revealing complex correlation effects.

Contribution

It provides detailed phase diagrams and insights into non-local correlation effects, including how they can induce metallic behavior in charge-ordered insulators.

Findings

Non-local correlations are significant in the uniform phase.

Near the phase transition, non-local interactions promote metallicity.

Strong non-local interactions can turn insulators into metals.

Abstract

We study the half filled extended Hubbard model on a two-dimensional square lattice using cluster dynamical mean field theory on clusters of size 8-20. We show that the model exhibits metallic, Mott insulating, and charge ordered phases, and determine the location of the charge ordering phase transition line and the properties of the ordered and disordered phase as a function of temperature, local interaction, and nearest neighbor interaction. We find strong non-local correlations in the uniform phase and a pronounced screening effect in the vicinity of the phase transition, where non-local interactions push the system towards metallic behavior. In contrast, correlations in the ordered phase are mostly local to the unit cell. Extrapolation to the thermodynamic limit and control of all sources of errors allow us to assess the regime of applicability of simpler approximation schemes for systems with non-local interactions. We also demonstrate how strong non-local electron-electron interactions can increase electron mobility by turning a charge ordered insulator into a metal.