Thermodynamics of the Generalized Spin-One-Half Falicov–Kimball Model in Two Dimensions

The extrapolation of small-cluster exact-diagonalization calculations and the Monte Carlo method is used to study the spin-one-half Falicov–Kimball model extended by the spin-dependent Coulomb interaction (J) between the localized f and itinerant d electrons as well as the on-site Coulomb interaction (Uff) between the localized f electrons. It is shown that in the symmetric case the ground-state phase diagram of the model has an extremely simple structure that consists of only two phases, and namely, the charge-density-wave phase and the spin-density-wave phase. The nonzero temperature studies showed that these phases persist also at finite temperatures. The same calculations that we performed for unsymmetric case showed that charge and spin ordering can be destroyed simultaneously or consecutively. PACS numbers: 75.10.Lp, 71.27.+a, 71.28.+d 1