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

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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≤2Δ(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.