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Condensed Matter Physics

LOCAL PAIRING IN THE ATTRACTIVE HUBBARD MODEL

S. Di Matteo, Mancini, Marra

Published Jan 1, 1996• 3 citations
Publisher

Abstract

this article we shall consider the case of the Hubbard model with on-site attraction. In Section 2 we derive the explicit expression for the Green's function, in the static approximation. In Section 3 we present some results for the double occupancy and the spin magnetic susceptibility for the case of half filling. By analytic method we can show that at zero temperature the system exhibits a phase transition to a pair state, where all the electrons are locally paired in a singlet state; the critical value U c for the interaction potential at which the phase transition occurs is equal to U c =-8t, 8t being the band width.

DOI
10.5488/cmp.8.109

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A one-dimensional lattice system of electrons with on-site (U) and bond-site (X) interactions is considered. Using the Green-function formalism in the Bloch representation, the occurrence of the possible instabilities in the ground state is analyzed within a mean-field-type approximation. At half filling, the X term does not modify the ground-state phase diagram of the Hubbard model; at lower (higher) band fillings a rather small bond-site attraction (repulsion) can favor the pairing of electrons.
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