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@PHDTHESIS{Gunel:153137,
      author       = {Gunel, Yusuf},
      title        = {{Q}uantum {T}ransport in {N}anowire-based {H}ybrid
                      {D}evices},
      school       = {RWTH Aachen},
      type         = {Dr.},
      reportid     = {FZJ-2014-02801},
      pages        = {170},
      year         = {2013},
      note         = {RWTH Aachen, Diss., 2013},
      abstract     = {We have studied the low-temperature transport properties of
                      nanowires contacted by a normal metal as well as by
                      superconducting electrodes. As a consequence of quantum
                      coherence, we have demonstrated the electron interference
                      effect in different aspects. The mesoscopic phase coherent
                      transport properties were studied by contacting the
                      semiconductor InAs and InSb nanowires with normal metal
                      electrodes. Moreover, we explored the interaction of the
                      microscopic quantum coherence of the nanowires with the
                      macroscopic quantum coherence of the superconductors. In
                      superconducting Nb contacted InAs nanowire junctions, we
                      have investigated the effect of temperature, magnetic field
                      and electric field on the supercurrent. Owing to relatively
                      high critical temperature of superconducting Nb
                      ($T_{c}\sim9\,$K), we have observed the supercurrent up to
                      4\,K for highly doped nanowire-based junctions, while for
                      low doped nanowire-based junctions a full control of the
                      supercurrent was achieved. Due to low transversal dimension
                      of the nanowires, we have found a monotonous decay of the
                      critical current in magnetic field dependent measurements.
                      The experimental results were analyzed within narrow
                      junction model which has been developed recently. At high
                      bias voltages, we have observed subharmonic energy gap
                      structures as a consequence of multiple Andreev reflection.
                      Some of the nanowires were etched, such that the
                      superconducting Nb electrodes are connected to both ends of
                      the nanowire rather than covering the surface of the
                      nanowire. As a result of well defined
                      nanowire-superconductor interfaces, we have examined
                      quasiparticle interference effect in magnetotransport
                      measurements. Furthermore, we have developed a new junction
                      geometry, such that one of the superconducting Nb electrodes
                      is replaced by a superconducting Al. Owing to the smaller
                      critical magnetic field of superconducting Al
                      ($B_{c}\sim15-50\,$mT), compared to superconducting Nb
                      ($B_{c}\sim3\,$T), we were able to studied the Andreev
                      reflection of quasiparticles at single interface, by
                      suppressing the superconductivity of Al with small magnetic
                      fields, as well as at double interface for zero magnetic
                      field. The junction geometry was further changed by
                      replacing the InAs nanowire with the InAs tube. In this case
                      the GaAs/InAs core/shell tubular nanowires were contacted by
                      two superconducting Nb electrodes. For this junction
                      geometry we have demonstrated the interference of phase
                      conjugated electron-hole pairs in the presence of coaxial
                      magnetic. The effect of temperature, constant dc bias
                      current and gate voltage on the magnetoresistance
                      oscillations were examined. In the last part of this thesis,
                      we have fabricated and characterized the single crystal Au
                      nanowire-based proximity superconducting quantum
                      interference device (SQUID).},
      keywords     = {Dissertation (GND)},
      cin          = {PGI-9},
      cid          = {I:(DE-Juel1)PGI-9-20110106},
      pnm          = {422 - Spin-based and quantum information (POF2-422)},
      pid          = {G:(DE-HGF)POF2-422},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/153137},
}