Nanometer SNS junctions as quantum-well devices

SNS junctions as electron-wave devices are studied both theoretically and experimentally. At zero bias voltage, the trajectory of quasiparticles bound in the well of pair potential is closed in the position-momentum space (x, p) and the area enclosed by the trajectory is an adiabatic invariant to be quantized. A very general program is developed to draw multiple Andreev reflections automatically in SNS structures at arbitrary bias voltages. The program teaches characteristics of the junctions are very sensitive to bias voltages especially across the subgap voltages V=2/spl Delta//ne.