Andreev scattering and cotunneling between two superconductor-normal metal interfaces: the dirty limit

Crossed Andreev reflections and cotunneling occur between two neighbouring superconductor- normal metal or superconducting-ferromagnet interfaces. Previous works assumed a clean BCS superconductor. Here the calculation of the corresponding crossed conductance terms is generalized to a dirty superconductor. The range of the effect is shown to be the coherence length , instead of the BCS coherence length . Moreover, in three dimensions, the algebraic prefactor scales as 1/r instead of 1/r ². The calculation involves the virtual diffusion probability of quasiparticles below the superconducting gap, in the normal and the anomalous channel.Received: 10 October 2003, Published online: 23 December 2003PACS: 74.45. + c Proximity effects; Andreev effect; SN and SNS junctions - 73.63.Rt Nanoscale contacts - 74.78.-w Superconducting films and low-dimensional structures