Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Transport: Poster Session

TT 22.4: Poster

Mittwoch, 27. Februar 2008, 14:00–18:00, Poster B

Non-equilibrium proximity effect in quantum dots — •Michele Governale¹, Marco G. Pala², and Jürgen König¹ — ¹Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44780 Bochum, Germany — ²IMEP-LAHC-MINATEC (UMR CNRS/INPG/UJF 5130), BP 257, F-38016 Grenoble, France

We present a real-time diagrammatic theory for transport through interacting quantum dots tunnel coupled to normal and superconducting leads [1]. We apply it to a system made up of a single-level quantum dot with Coulomb interaction, coupled to one normal and two superconducting leads. A finite bias voltage can be applied to the normal lead to drive the dot out of equilibrium. We compute both the Andreev current in the normal lead and the Josephson current between the two superconductors. In the large-superconducting-gap limit, we are able to calculate the non-equilibrium Andreev and Josephson currents to all orders in the tunnel coupling with the superconducting leads. In particular, we show that a spectroscopy of the Andreev bound states in the dot can be performed by measuring the current in the normal lead as a function of the dot level position and of the bias voltage. Furthermore, we identify the regions of bias and gate voltage where the system behaves as a π-junction.

[1] M. G. Pala, M. Governale, and J. König, New J. Phys. 9, 278 (2007).