Conductance enhancement in quantum-point-contact semiconductor-superconductor devices

Asger Mortensen, Antti-Pekka Jauho, Karsten Flensberg, Henning Schomerus

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    Abstract

    We present numerical calculations of the conductance of an interface between a phase-coherent two-dimensional electron gas and a superconductor with a quantum point contact in the normal region. Using a scattering matrix approach we reconsider the geometry of De Raedt, Michielsen, and Klapwijk [Phys. Rev. B 50, 631 (1994)] which was studied within the time-dependent Bogoliubov-de Gennes formalism. We find that the factor-of-2 enhancement of the conductance G(NS) compared to the normal state conductance GN for ideal interfaces may be suppressed for interfaces with a quantum point contact with only a few propagating modes. The suppression is found to depend strongly on the position of the Fermi level. We also study the suppression due to a barrier at the interface and find an anomalous behavior caused by quasiparticle interference. Finally, we consider the limit of sequential tunneling and find a suppression of the factor-of-2 enhancement which may explain the absence of conductance enhanced in experiments on metal-superconductor structures. [S0163-1829(99)07943-6].
    Original languageEnglish
    JournalPhysical Review B
    Volume60
    Issue number19
    Pages (from-to)13762-13769
    ISSN2469-9950
    DOIs
    Publication statusPublished - 1999

    Bibliographical note

    Copyright (1999) by the American Physical Society.

    Keywords

    • FLUCTUATIONS
    • METAL
    • JOSEPHSON-JUNCTIONS
    • TRANSPORT
    • NANOSTRUCTURES
    • CONSTRICTION
    • SUPERCURRENT
    • QUANTIZED CONDUCTANCE
    • RESISTANCE
    • ANDREEV REFLECTION

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