Field theory of mesoscopic fluctuations in superconductor-normal-metal systems

Thermodynamic and transport properties of mesoscopic conductors are strongl y influenced by the proximity of a superconductor: an interplay between the large scale quantum coherent wave functions in the normal mesoscopic and t he superconducting region, respectively, leads to unusual mechanisms of qua ntum interference. These manifest themselves in both the mean and the mesos copic fluctuation behaviour of superconductor-normal-metal (SN) hybrid syst ems being strikingly different from those of conventional mesoscopic system s. After reviewing some established theories of SN quantum interference phe nomena, we introduce a new approach to the analysis of SN mesoscopic physic s. Essentially, our formalism represents a unification of the quasi-classic al formalism for describing mean properties of SN systems on the one hand, with more recent field theories of mesoscopic fluctuations on the other han d. Thus, by its very construction, the new approach is capable of exploring both averaged and fluctuation properties of SN systems on the same microsc opic footing. As an example, the method is applied to the study of various characteristics of the single particle spectrum of SNS structures.