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

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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 Ef, where they lead to: (i) stabilization of the ferroelectric ground state with a spontaneous hybridization Pdf= d+f 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. t'd < 0, The effects of correlated hopping on valence transitions are also discussed.