MESOSCOPIC TRANSPORT IN TUNABLE ANDREEV INTERFEROMETERS

Low temperature transport measurements have been performed on nanofabricated Au wires a few mu m long contacting two Nb electrodes whose superconducting phase difference Delta theta was externally controlled. Delta theta was generated by passing a known supercurrent through a series array of 28 Nb-AlOx- Nb Josephson junctions. The conductance of the Au wire displays a component in Delta theta with period 2 pi. These conductance oscillations arise from the change in scattering boundary conditions of quasiparticles in the Au wire at the Au-Nb interfaces due to Andreev reflection.