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  • 74.50  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 97 (1995), S. 59-66 
    ISSN: 1434-6036
    Keywords: 74.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The present paper is a continuation of [1], where we demonstrated the occurrence of multiple Andreev-reflection (AR) in symmetric Pb/n-InSb/Pb sandwich junctions. Here we are presenting the results of our investigations for the asymmetric configuration Pb/n-InSb/Sn. We discuss the measuredI(V)- anddV/dI(V)-characteristics in comparison with numerical calculations, which we carried out in a theoretical extension of the OTBK-theory [2,3] and a formulation given by W.M. van Huffelen et al. [4]. The main features in the characteristics are thesubharmonic gap structure (SGS) and anexcess current, which show interesting deviations from the symmetric situation. These deviations can be understood in a simple physical picture.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 94 (1994), S. 21-28 
    ISSN: 1434-6036
    Keywords: 74.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mechanically point contacts made of Ta, Al, Ag (anvil) and of Ta, Ag (needle) were investigated in the temperature range between 4.2 K and 1.3 K and in magnetic fields up to 0.8 T. For point contacts consisting of two superconducting electrodes we measured the current voltage characteristics and also the dynamic conductance. The characteristics with a negative differential conductance and the occurrence of an excess current point to the appearance of Andreev-multiple reflection at an SNS-interface in the contact region. The investigated current voltage characteristics and the dynamic conductance of typical NS-point contacts (Ta−Ag and Ta−Al) point to a microconstriction with a barrier of arbitrary strength at the interface between the normalconductor and the superconductor. We performed theoretical calculations forT=0 and also for temperatures up to the critical temperature using the model of Blonder, Tinkham and Klapwijk (BTK model). In this model the Andreev-reflection is the main scattering mechanism at the NS-interface but also elastic scattering and transmission processes are taken into consideration. The comparison of our theoretical results with the experimental results and also the determined excess current at all investigated point contacts lead to the assumption that there exist metallic contacts with very small barrier strengths at the NS-interface where the Andreev-reflection is the dominant process and the other scattering mechanisms play a subdominant role.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 92 (1993), S. 187-190 
    ISSN: 1434-6036
    Keywords: 74.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We studied the carrier transport through n-InSb-films sandwiched between two superconducting lead electrodes. These n-InSb-films were about 30 nm thick, polycrystalline and very highly doped (1021 cm−3). TheV(I)- and dV/dI (V)-characteristics indicated all the properties of Andreev-reflection (subharmonic energygap structures (SGS) and excess current) according to the theory of Octavio et al. (OTBK-model) [1, 2]. Our measurements show the temperature dependence of these structures and also the influence of magnetic fields up to 80 mT and give a further reference to the importance of Andreev-reflection in semiconductor-coupled superconducting junctions (SSmS junctions).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 96 (1994), S. 13-24 
    ISSN: 1434-6036
    Keywords: 74.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigated the carrier transport through highly dopedn—InSb-films sandwiched between two superconducting lead electrodes. The measuredI(V)- anddV/dI(V)-characteristics show a very clear subharmonic gap structure (SGS) and an excess current, indicating the occurrence of multiple Andreev-reflection between the two semiconductor-superconductor interfaces. For the theoretical background we consult the theory of Octavio et al. (OTBK-model). We show that the application of this theory leads to some difficulties. According to this we propose some modifications, which in our opinion give a better description of the real situation in such contacts. We calculated theI(V)- anddV/dI(V)-characteristics of junctions with dissimilar barrier strength at the two interfaces as well as such for different superconductors, and compare these results with the experimental observations. We studied the influence of electromagnetic radiation on the junctions properties experimentally as well as theoretically for frequencies ranging in the classical limit. Moreover we evaluate the temperature dependence of the excess current, compare it with theoretical results and give an estimation of the barrier strength. The critical current is studied in dependence on the temperature and in comparison with calculations of Kuprianov and Lukichev (KL-theory), as well as under rf-application.
    Type of Medium: Electronic Resource
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