Coulomb Correlations and the Wigner-Mott Transition

TL;DR

This paper demonstrates that strong Coulomb correlations can induce a Wigner-Mott transition even away from integer filling, explaining experimental observations in low-density electron gases through an extended Hubbard model analysis.

Contribution

It introduces a mechanism where non-local Coulomb interactions enhance correlations far from integer filling, unifying Wigner and Mott transition perspectives.

Findings

Correlation effects explain metal-insulator transitions in dilute electron gases.

Spectral function should show a three-peak structure due to charge order and local correlations.

The model accounts for experimental phase diagrams of low-density electron systems.

Abstract

Strong correlation effects, such as a dramatic increase in the effective mass of the carriers of electricity, recently observed in the low density electron gas have provided spectacular support for the existence of a sharp metal-insulator transitions in dilute two dimensional electron gases. Here we show that strong correlations, normally expected only for narrow integer filled bands, can be effectively enhanced even far away from integer filling, due to incipient charge ordering driven by non-local Coulomb interactions. This general mechanism is illustrated by solving an extended Hubbard model using dynamical mean-field theory. Our findings account for the key aspects of the experimental phase diagram, and reconcile the early view points of Wigner and Mott. The interplay of short range charge order and local correlations should result in a three peak structure in the spectral function of the electrons which should be observable in tunneling and optical spectroscopy.