Physical review. B, Condensed matter

Exact solution of a periodic-cluster Hubbard model with an electron-lattice interaction

César R. Proetto, L. M. Falicov

Published Jul 15, 1988• 9 citations

Abstract

An exact solution of a modified Hubbard model for a tetrahedral cluster with periodic boundary conditions is presented. It includes a static electron-lattice interaction in which the intersite bond-hopping parameter is a function of the bond electron occupation. It is found that the intrasite Coulomb repulsion and the effective attractive electron-lattice interaction have, generally speaking, opposite (although not identical) effects. They cancel each other exactly along a line of singularities in parameter space. The state vectors are easily obtained analytically. A study is made of magnetic and superconducting static correlation functions as functions of the parameters. Various forms of anisotropic superconducting fluctuations are favored in the various regimes. There is an indication of possible states with coexisting nonuniform, nonisotropic superconductivity and antiferromagnetism caused by a ``compromise'' between the competing forces.

DOI: 10.1103/physrevb.38.1754

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