QUASI-PARTICLE DISTRIBUTION IN A SUPERCONDUCTOR NORMAL-MATERIAL SUPERCONDUCTOR JUNCTION IN THE CLEAN LIMIT

In order to study the spatial distribution of quasiparticles in a superconductor-normal-metal-superconductor (S / N / S) junction, the tunneling conductance dI / dV is calculated with use of a pair potential determined self-consistently in numerical calculations. The interference between electron-like and holelike quasiparticles is found to cause a spatial change of dI / dV in the N region, the scale of which is of order of the decay length of the pair potential. For an attractive interelectron potential in the N region, quasiparticles with energy below the bound state are predominantly found in the middle of the N region; for a repulsive interelectron potential, they are predominantly found at the interface. The sign of the interelectron potential in the N region can be distinguished by performing a scanning-tunneling-microscopy experiment in which both S and N materials have nearly equal Fermi momenta.