Theory of Superconductors with Overlapping Bands in the Presence of Nonmagnetic Impurities

Publisher Website
Google Scholar
Abstract
The two-band model proposed by Suhl, Matthias, and Walker (SMW) for the superconducting state of pure transition metals is extended to the transition metals in the presence of nonmagnetic impurities. Both the interband and intraband impurity scattering are included in the formulation of the extended model. Two limiting cases of the extended model, namely, the strong intraband phonon-coupling limit and the strong interband phonon-coupling limit, are studied in detail. The basic features of the two limiting cases agree with those of the SMW model. It is found that, in the case of the strong intraband phonon-coupling limit, the lower one of the two transition temperatures is raised from that of the SMW model by the interband impurity scattering, and, in the case of the strong interband phonon-coupling limit, the transition temperature is either raised or lowered from that of the SMW model, depending on whether the interband impurity scattering or the intraband impurity scattering is stronger.