Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: Superconductivity - Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 9.5: Talk

Monday, March 26, 2007, 17:30–17:45, H20

Supercurrent through Semiconductor Quantum Wells in Parallel Magnetic Fields — •Franziksa Rohlfing¹, Thomas Geiger¹, Grigory Tkachov², Gustaaf Borghs³, Christoph Strunk¹, and Dieter Weiss¹ — ¹Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Germany — ²Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — ³IMEC, Leuven, Belgium

We investigate the transport properties through narrow InAs bridges in a 4-point configuration within the two-dimensional electron gas (2DEG), that is formed in the InAs inversion layer. Superconductivity is proximity induced into the 2DEG by two sputterdeposited niobium stripes across the bridge. In this way a ballistic Josephson junction is formed within the 2DEG. The critical current of these junctions is measured as a function of perpendicular and parallel magnetic field. In a magnetic field perpendicular to the 2DEG the well-defined Fraunhofer pattern is observed. On the other hand, when the 2DEG is oriented parallel to the magnetic field, a monotonic decay of the critical current is observed. The measurement data can be explained within the framework of two models that discuss the effect of the Doppler shift or the Zeeman splitting on the Andreev bound states, respectively.