Mean-field theory of high-T/sub c/ superconductivity: The superexchange mechanism

We develop the simplest mean-field theory of an extended Hubbard model in the limit of a large intrasite Coulomb interaction, concentrating on the possibility of superconductivity induced by the superexchange interaction and weakened by the intersite Coulomb repulsion. We calculate the critical temperature and the coherence length as a function of filling, as well as the temperature dependence of the magnetic susceptibility and specific heat. Finally, we comment on the physics of the insulating state at half filling, and mention the probable effects of fluctuations