Nonlinear sigma model for disordered superconductors - art. no. 064522

We suggest a variant of the nonlinear sigma model for the description of di sordered superconductors. The main distinction from existing models lies in the fact that the saddle point equation is solved nonperturbatively in the superconducting pairing field. It allows one to use the model both in the vicinity of the metal-superconductor transition and well below its critical temperature with full account for the self-consistency conditions. We show that the model reproduces a set of known results in different limiting cas es, and apply it for a self-consistent description of the proximity effect at the superconductor-metal interface.