The role of the surface depression of the pair potential on the Josephson and quasi-particle tunnelling in high-T c superconductors

Abstract

We discuss the influence of the intrinsic surface depression of the order parameter on the temperature dependence of the Josephson critical currentI c(T) and, tentatively, on the quasi-particle tunnelling conductance in a superconductor with a very short coherence length. The comparison with the experiments shows that the presence of a surface-depressed pair potential can explain the large deviations of theI c(T) from the ideal BCS behaviour that we recently observed in Bi2Sr2CaCu2O8+x Josephson break junctions and could mimic the presence of a broadening in the Superconductor-Insulator-Normal tunnelling conductance of the same high-T c superconductor.