title: Crossover from Josephson effect to single interface Andreev reflection in asymmetric superconductor/nanowire junctions.
abstract: We report on the fabrication and characterization of symmetric nanowire-based Josephson junctions, that is, Al- and Nb-based junctions, and asymmetric junctions employing superconducting Al and Nb. In the symmetric junctions, a clear and pronounced Josephson supercurrent is observed. These samples also show clear signatures of subharmonic gap structures. At zero magnetic field, a Josephson coupling is found for the asymmetric Al/InAs-nanowire/Nb junctions as well. By applying a magnetic field above the critical field of Al or by raising the temperature above the critical temperature of Al the junction can be switched to an effective single-interface superconductor/nanowire structure. In this regime, a pronounced zero-bias conductance peak due to reflectionless tunneling has been observed.
authors.affiliation: Peter Grünberg Institute (PGI-9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors.forename: H Y
authors.initials: HY
authors.lastname: Günel
authors.forename: N
authors.initials: N
authors.lastname: Borgwardt
authors.forename: I E
authors.initials: IE
authors.lastname: Batov
authors.forename: H
authors.initials: H
authors.lastname: Hardtdegen
authors.forename: K
authors.initials: K
authors.lastname: Sladek
authors.forename: G
authors.initials: G
authors.lastname: Panaitov
authors.forename: D
authors.initials: D
authors.lastname: Grützmacher
authors.forename: Th
authors.initials: T
authors.lastname: Schäpers
keywords: Andreev reflection; InAs nanowire; Josephson effect; asymmetric junctions; reflectionless tunneling; superconducting electrodes