Competing Orderings in an Extended Falicov-Kimball Model

TL;DR

This study investigates how on-site and non-local hybridization affect excitonic effects and charge-density wave stability in an extended Falicov-Kimball model, revealing different impacts on excitonic correlations.

Contribution

It provides a Hartree-Fock analysis of hybridization effects on excitonic and CDW states, including a Ginzburg-Landau phenomenological approach, highlighting distinct behaviors for on-site and non-local hybridization.

Findings

CDW state remains stable with finite hybridization

Coulomb interaction enhances excitonic average with on-site hybridization

Non-local hybridization suppresses excitonic correlations

Abstract

We present a Hartree-Fock study of the Falicov-Kimball model extended by both on-site and non-local hybridization. We examine the interplay between excitonic effects and the charge-density wave (CDW) instability known to exist at zero hybridization. It is found that the CDW state remains stable in the presence of finite hybridization; for on-site hybridization the Coulomb interaction nevertheless strongly enhances the excitonic average above its value in the noninteracting system. In contrast, for non-local hybridization, we observe no such enhancement of the excitonic average or a spontaneous on-site hybridization potential. Instead, we find only a significant suppression of the excitonic correlations in the CDW state. A phenomenological Ginzburg-Landau analysis is also provided to understand the interplay.