Simulations of experimental conductance spectra of $YBa_2Cu_3O_y$ junctions: Role of a long d-wave decay length and a small $is$ component in the pair potential near the interface

Abstract

Extended BTK-type theoretical methods were used for the calculation of conductance spectra of NS and NIS junctions, where S is either a d-wave or a d+is-wave superconductor, and N is a normal metal. We found that the length scale over which the bulk d-wave order parameter varies spatially near the interface (the "decay length") has a significant effect on the main features of the conductance spectra. A relatively large decay length of the order of 10-20$\xi_{0}$ together with a small $is$-wave component, can explain many peculiarities observed in the experimental conductance spectra of various junctions. We attribute the long decay length to either a reversed proximity effect in the high transparency junctions, or to the presence of a low $T_c\leq 10$K s-wave component with a much longer $\xi_{0s}\approx 10\xi_{0d}$ near the interface.