Ground States of the Falicov-Kimball Model Extended by Nonlocal Coulomb Interactions

H. Čenčariková, P. Farkašovský and M. Žonda Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 041 01 Košice

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Received: 9 07 2007;

The small-cluster exact-diagonalizations are used to study the ground states of the Falicov-Kimball model extended by nonlocal Coulomb interactions (the nearest-neighbour interaction Unn and the correlated hopping t'). It is shown that the ground-state phase diagrams found for the conventional Falicov-Kimball model are strongly changed when the nonlocal interactions are added. This is illustrated for two selected values of the on-site Coulomb interaction (U) that represent typical behaviours of the model in the intermediate and strong coupling limit. A number of remarkable results are found. (i) The phase separation takes place for a wide range of Unn and t' in both interaction limits. (ii) New types of inhomogeneous charge ordering are observed for nonzero Unn and t'. (iii) Depending on the values of Unn and t', the model is able to describe both the continuous as well as discontinuous changes of the f-electron occupation number.

DOI: 10.12693/APhysPolA.113.287 PACS numbers: 75.10.Lp, 71.27.+a, 71.28.+d