Perturbation theory for the periodic Anderson model: II. Superconducting state

A new diagram technique, which has been developed for strongly correlated electron systems, is used to study the periodic Anderson model in the superconducting state. To treat both normal and anomalous Green's functions on an equal footing, we introduce an additional charge quantum number that distinguishes creation and annihilation operators. We derive the Dyson equations for the Green's functions of band and localized electrons in the presence of superconductivity. The equations obtained admit both singlet-type and triplet-type superconductivity. For singlet-type superconductivity, we establish the correspondence between these equations and the spinor Gor'kov–Nambu formalism.