CURRENT-CARRYING STATES IN SUPERCONDUCTING MULTILAYERS WITH JOSEPHSONINTERLAYER COUPLING FOR TEMPERATURES CLOSE TO T-C0 - A MICROSCOPIC THEORY

We present a complete, self-consistent, microscopic description of cur rent-carrying states in all sorts of superconducting multilayers with interlayer Josephson coupling near the bulk critical temperature, T-c0 : superconductor-insulator (SI) superlattices with or without intrabar rier exchange interactions and nonmagnetic impurities inside supercond ucting (S) layers, pure structures with point-contact-type interlayer coupling, superconductor-normal-metal (SN) superlattices with an arbit rary concentration of nonmagnetic impurities. and SN superlattices in the dirty limit with paramagnetic impurities inside N barriers. We hav e obtained closed analytical expressions for the Josephson current as a function of an S layer thickness, a. For all these systems drastic d eviations from a single-junction case were found: a reduction of the c ritical Josephson current j(c) for pure SI superlattices with a less t han or equal to xi(0), nontrivial current-phase dependence for multila yers with point-contact-type coupling and a less than or equal to xi(0 ), and nontrivial temperature dependence of j(c) for SN superlattices, Mathematically, our approach is based solely on the use of a microsco pic free-energy functional. For a much greater than xi(0), we reduce t his functional to a Ginzburg-Landau-type functional with an extra term accounting for the interface free energy. For SI superlattices, in an appropriate limit this latter reduces to a Lawrence-Doniach-type func tional with microscopically defined coefficients.