Andreev reflection current in clean and one-dimensional Nb short weak links

Nb-(fine Nb wires)-NbN short weak links (SWLs) have been reproducibly fabricated by the field evaporation technique. By this method, one could continuously vary the I-V curve from insulator type to tunnel-type to metallic-contact type. The quasiparticle characteristics are qualitatively very similar to the prediction of Klapwijk, Blonder, and Tinkham (KBT) theory for the simple case of two independent normal metal-superconductor interfaces in the clean contact limit.<
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