Dresden 2003 – wissenschaftliches Programm

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SYHN: Hybrid nanostructures

SYHN 1: Hybrid Nanostructures

SYHN 1.5: Hauptvortrag

Donnerstag, 27. März 2003, 11:40–12:05, HSZ/01

Phase-coherent Andreev reflection in superconductor/semiconductor junctions — •Thomas Schäpers, V.A. Guzenko, R.A. Müller, and A. Kaluza — Institut für Schichten und Grenzflächen, Forschungszentrum Jülich GmbH, 52425 Jülich

Multi-terminal Josephson junctions containing additional normal contacts can be used as a versatile tool to investigate Andreev reflection processes. In order to achieve ballistic transport, a two-dimensional electron gas in an InGaAs/InP heterostructure is employed as a normal conductor, while the superconducting electrodes are based on Nb. By injecting hot carriers from a normal contact, the supercurrent can be controlled. The underlying mechanism can be explained by the modification of the occupation of Andreev bound states. In addition, multi-terminal junctions can also be operated in an opposite mode where the conductance between the normal contact and one superconducting electrode is controlled by quasiparticle interference effects which are induced by the Josephson effect. In contrast to experiments where the phase difference between two superconducting terminals is adjusted by a flux in a superconducting coil, we made use of the phase control by the Josephson supercurrent. The quasiparticle interference results in a conductance plateau with a maximum at zero bias current through the Josephson junction. The experimental results are explained by a model taking phase-coherent Andreev reflection into account. By applying an additional external magnetic field the interference effects can be modified.