Effects of correlated hopping on electronic ferroelectricity in the extended Falicov-Kimball model in two dimensions

TL;DR

This study investigates how correlated hopping influences electronic ferroelectricity in the two-dimensional extended Falicov-Kimball model, revealing strong effects that stabilize or suppress ferroelectric phases depending on the correlated hopping parameters.

Contribution

It demonstrates the significant impact of correlated hopping on ferroelectric and antiferroelectric stability within the extended Falicov-Kimball model using Hartree-Fock approximation.

Findings

Correlated hopping stabilizes ferroelectric ground state for positive hopping parameters.

It induces antiferroelectric phases for certain negative hopping values.

Correlated hopping can suppress ferroelectricity depending on parameter values.

Abstract

We use the Hartree-Fock (HF) approximation with the charge-density-wave (CDW) instability to study the effect of correlated hopping on the stability of electronic ferroelectricity in the extended Falicov-Kimball model (FKM) in two dimensions. It is shown that the effects of correlated hopping term are very strong, especially for negative values of the $f$-level energy $E_f$, where they lead to: (i) stabilization of the ferroelectric ground state with a spontaneous hybridization $P_{df}=\langle d^+f \rangle$ for positive values of correlated hopping parameter $t'_d$, (ii) stabilization of the antiferroelectric phase for $t'_d < t'_{d,crit.} < 0$ and (iii) suppression of the ferroelectric ground state for $t'_{d,crit.} \leqslant t'_d < 0$, The effects of correlated hopping on valence transitions are also discussed.