Mesoscopic Giaever and Josephson junctions

Quasi-particle wave interference controls both the current-characteristics and the current-relation of a superconducting device. To illustrate this point, we show that both the Josephson current-relation I(φ)=Icsin(φ) and the nonlinear current-voltage characteristic known as Giaever tunneling can be understood only through mesoscopic processes occurring at the interface to the superconductor. The critical current through a one-dimensional superconducting wire or point contact, which has order of magnitude eΔ/h, is a measure of Landau's superfluid depairing velocity Δ/pF. ((orig.))