Electron transport in normal-metal/superconductor junctions
Abstract
On the basis of the Keldysh method of nonequilibrium systems, we develop a theory of electron tunneling in normal-metal-superconductor junctions. By using the tunneling Hamiltonian model (being appropriate for the tight-binding systems), the tunneling current can be exactly obtained in terms of the equilibrium Green functions of the normal metal and the superconductor. We calculate the conductance of various junctions. The discrepancy bt:tween the present treatment and the well-known scheme by Blender, Tinkham, and Klapwijk is found for some junctions of low interfacial potential barrier.