MULTIPLE ANDREEV SCATTERING IN SUPERCONDUCTOR NORMAL-METAL SUPERCONDUCTOR JUNCTIONS AS A TEST FOR ANISOTROPIC ELECTRON PAIRING

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 less-than-or-equal-to 2DELTA(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.