Extended Hubbard model: Charge Ordering and Wigner-Mott transition

TL;DR

This paper investigates how inter-site Coulomb interactions in the extended Hubbard model lead to charge ordering and a Wigner-Mott transition, revealing complex intermediate regimes with enhanced correlations relevant to low-density electron systems.

Contribution

It provides a detailed analysis of charge ordering and Wigner-Mott transition phenomena in the quarter-filled extended Hubbard model, highlighting the emergence of an intermediate correlated regime.

Findings

Charge ordering occurs away from half-filling due to inter-site Coulomb repulsion.

An intermediate regime with large mass enhancements and strong correlations is identified.

Relevance to low-density two-dimensional electron gases is discussed.

Abstract

Strong correlation effects, which are often associated to the approach to a Mott insulating state, in some cases may be observed even far from half-filling. This typically happens whenever the inter-site Coulomb repulsion induces a tendency towards charge ordering, an effect that confines the electrons, and in turn favors local moment formation, i.e. Mott localization. A distinct intermediate regime then emerges as a precursor of such a Wigner-Mott transition, which is characterized by both charge and spin correlations, displaying large mass enhancements and strong renormalizations of other Fermi liquid parameters. Here we present a careful study of a quarter filled extended Hubbard model - a simple example where such physics can be studied in detail, and discuss its relevance for the understanding of the phenomenology of low-density two dimensional electron gases.