SADDLE-POINT PAIRING - AN ELECTRONIC MECHANISM FOR SUPERCONDUCTIVITY

It is shown that the interactions in a strongly correlated quasi-two-dimensional electron gas with the Fermi level lying at a saddle point (Van Hove singularity) in epsilon(k) can give rise to superconductivity by exchange of excitations with a characteristic low electronic energy scale E*. Application to cuprate superconductors shows that this mechanism along with a conventional electron-phonon interaction can explain the high T(c)'s and the anomalous behavior of the isotope shift as a function of doping.