Quasiclassical Green's function approach to mesoscopic superconductivity
  Recent experiments on mesoscopic normal-metal--superconductor heterostructures resolve properties on length scales and at low temperatures such that the temperature is below the Thouless energy $k_B T \le E_{Th}$. We describe the properties of these systems within the framework of quasiclassical many-body techniques. Diffusive and ballistic systems are covered, both in equilibrium and nonequilibrium situations. Thereby we demonstrate the common physical basis of various subtopics. 
Wolfgang Belzig, Frank K. Wilhelm, Christoph Bruder, Gerd Sch\"on, and   Andrei D.Zaikin (Institut f\"ur Theoretische Festk\...