Quasiparticle conduction in mesoscopic wires containing N-S-N junctions

Abstract

We measured the dynamic resistance (dV/dl) of mesoscopic normal-metal/superconductor/normal-metal (N-S-N) junctions. At low temperatures (T < 4 K), we observed dips in dV/dI at zero bias and anomalous peaks near the bias of 2 Delta(PbIn)/e (where 2 Delta(PbIn) is the gap energy of superconducting Pb-ln) and at higher bias V-c. The zero-bias dips are supposed to originate from Andreev reflections of electrons and the peaks near 2 Delta(PbIn)/e from the interference of quasiparticles inside S. We attribute the peaks at V-c to the transition of the superconducting region to the normal state as the current exceeds the critical current I-c of S.