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Abstract:
The properties of systems consisting of a mixture of local
electron pairs and itinerant fermions coupled via charge
exchange mechanism, which mutually induces superconductivity in
both subsystems, are analyzed. The case of anisotropic pairing
of various symmetries is discussed in detail for a two-
dimensional (2D) square lattice within the BCS-mean field
approximation and the Kosterlitz-Thouless theory. The effects
of electronic band dispersion as well as a quasi-2D case with
interplanar hopping of electrons are also briefly analyzed. We
determined the phase diagrams and superconducting
characteristics as a function of the position of the local pair
(LP) level and the total electron concentration. The possible
types of crossovers from BCS like behavior to that of LP's are
examined. In addition, the Uemura plots are obtained for
extended s and d(x)(2)-y(2) pairing symmetries. Some of our
findings are discussed in connection with a two-component
scenario of preformed pairs and unpaired electrons for the
cuprate high-temperature superconductors.
