Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 26: Superconductivity - Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 26.3: Vortrag

Dienstag, 8. März 2005, 10:45–11:00, TU H3027

Andreev reflection in hybrid InGaAs/InP structures with superconducting NbN contacts — •I. E. Batov¹, Th. Schäpers², A. A. Golubov³, and A. V. Ustinov¹ — ¹Physikalisches Institut III, Universität Erlangen-Nürnberg — ²ISG-1, Forschungszentrum Jülich — ³Faculty of Applied Physics, University of Twente, The Netherlands

We have studied magnetotransport and differential current voltage characteristics of highly transparent superconductor/normal metal/two-dimensional electron gas junctions formed by a superconducting NbN electrode, a thin (10nm) Au interlayer, and a two-dimensional electron gas in an InGaAs/InP heterostructure. A decrease in the differential resistance with pronounced double dip structure has been observed within the superconducting energy gap. It is argued that the double-dip structure in the differential resistance is related to the transport in SN-2DEG contacts in the ballistic regime. It has been found that the reduced subgap resistance is preserved in high quantizing magnetic fields. We observed resistance oscillations as a function of magnetic field at zero dc bias current in our junctions. The effect of temperature and dc bias current on the amplitude of the magnetoresistance oscillations was studied. The experimental results are qualitatively explained by taking Andreev reflection in high magnetic fields into account.