Effect of impurity scattering on the critical temperature of superconductors with partial dielectrization of the electron spectrum

The effect of the scattering potential of nonmagnetic or magnetic impurities on the critical superconducting temperature T/sub c/ is considered for superconductors with partial or total dielectrization of the electron spectrum. It is shown that T/sub c/ increases with increase of the nonmagnetic impurity density, i.e., the Anderson theorem does not hold for such systems. Scattering by magnetic impurities lowers T/sub c/. The decrease, however, is weaker than in ordinary superconductors, owing to the presence of a dielectric gap Σ on the Fermi surface