DDW Order and its Role in the Phase Diagram of Extended Hubbard Models

TL;DR

This paper demonstrates through mean-field calculations that extended Hubbard models can produce phase diagrams with DDW order, coexisting with AF and superconductivity, resembling those observed in cuprate superconductors.

Contribution

It shows that simple microscopic models can generate complex phase diagrams with DDW order, providing insights into cuprate phenomenology.

Findings

DDW order appears in the underdoped region.

Coexistence of DDW with AF and DSC observed.

Phase diagrams depend on coupling constants.

Abstract

We show in a mean-field calculation that phase diagrams remarkably similar to those recently proposed for the cuprates arise in simple microscopic models of interacting electrons near half-filling. The models are extended Hubbard models with nearest neighbor interaction and correlated hopping. The underdoped region of the phase diagram features $d_{{x^2}-{y^2}}$ density-wave (DDW) order. In a certain regime of temperature and doping, DDW order coexists with antiferromagnetic (AF) order. For larger doping, it coexists with $d_{{x^2}-{y^2}}$ superconductivity (DSC). While phase diagrams of this form are robust, they are not inevitable. For other reasonable values of the coupling constants, drastically different phase diagrams are obtained. We comment on implications for the cuprates.