CURRENT-INDUCED BOUND-STATES IN SUPERCONDUCTING JUNCTIONS OF FINITE DIMENSION

In this paper. we study theoretically the effect of geometric factors on the recently predicted quasiparticle bound states induced by superc urrent in superconducting point contacts and tunnel junctions. We deri ve a general formula for the energy of the bound state in a finite-siz e junction with a barrier of arbitrary strength at the interface. We s how that the energy of the bound state is a rapidly oscillating functi on of the linear dimension of the junction in the direction perpendicu lar to the interface, L. As a result, the density of quasiparticle sta tes in the gap region after averaging over fluctuations of L on the at omic scale has a band-type feature analogous to that predicted for a S /I superlattice in the current-carrying: state.