Ground-state properties of the Falicov-Kimball model with correlated hopping in two dimensions

A new numerical method, recently developed to study ground states of the Falicov-Kimball model (FKM), is used to examine the effects of correlated hopping on the ground-state properties of this model in two dimensions. It is shown that the ground-state phase diagram as well as the picture of metal-insulator transitions found for the conventional FKM (without correlated hopping) are strongly changed when the correlated hopping term is added. The effect of correlated hopping is so strong that it can induce the insulator-metal transition, even in the strong-coupling limit, where the ground states of the conventional FKM are insulating for all $f$-electron densities.Comment: 11 pages, 2 figures, LaTe

Formation of charge and spin ordering in strongly correlated electron systems

In this review we present results of our theoretical study of charge and spin ordering in strongly correlated electron systems obtained within various generalizations of the Falicov-Kimball model. The primary goal of this study was to identify crucial interactions that lead to the stabilization of various types of charge ordering in these systems, like the axial striped ordering, diagonal striped ordering, phase-separated ordering, phase-segregated ordering, etc. Among the major interactions that come into account, we have examined the effect of local Coulomb interaction between localized and itinerant electrons, long-range and correlated hopping of itinerant electrons, long-range Coulomb interaction between localized and itinerant electrons, local Coulomb interaction between itinerant electrons, local Coulomb interaction between localized electrons, spin-dependent interaction between localized and itinerant electrons, both for zero and nonzero temperatures, as well as for doped and undoped systems. Finally, the relevance of resultant solutions for a description of rare-earth and transition-metal compounds is discussed.Comment: 66 pages, 65 figure

Insulator-to-metal crossover induced by local spin fluctuations in strongly correlated systems

We study the simplified Hubbard (SH) model in the presence of a transverse field in the infinite dimension limit. The relevant one-particle Green's functions of the model are obtained by means a perturbative treatment of the hopping and of the transverse field around the atomic limit. We consider an analytical solution for the impurity problem. It is shown that this solution is very accurate in describing the spectral properties of the heavy-particles of the SH for intermediate and strong values of the on-site Coulomb interaction $U$. We find that for large values of $U$ an insulator-metal transition takes place as a function of the transverse field. We analyze the metallic phase through the behavior of the density of states and of the optical conductivity and static resistivity. Our results for the latter quantity agree with what is observed in experiments on $Bi_2Sr_2CuO_y$.Comment: 6 pages, 5 figures, to appear in Journal of Physics: Condensed Matte