Multiple Andreev scattering in superconductor–normal metal–superconductor junctions as a test for anisotropic electron pairing

Abstract

Current-voltage characteristics of superconductor--normal metal--superconductor junctions due to multiple Andreev reflections at the interfaces are investigated for anisotropic superconductors. Using nonequilibrium time-dependent Bogoliubov--de Gennes equations, it is shown that the presence of gap nodes perpendicular to the interface greatly smear subharmonic gap structures corresponding to voltages V\ensuremath{\le}2\ensuremath{\Delta}(k^)/en for n=1,2,3,. . . for n Andreev reflections as seen in s-wave superconductors, while the overall current due to Andreev reflections is reduced. Further, asymmetric line shapes for dI/dV are predicted. It is suggested that these features could be used to distinguish between superconductors with or without nodes.