Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.54: Poster

Mittwoch, 28. März 2012, 15:00–19:00, Poster B

Nonequilibrium Josephson and quasi-particle currents through hybrid superconductor-quantum dot devices — •Sascha Ratz and Milena Grifoni — Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany

We present a real-time diagrammatic theory for investigating the Josephson current through an interacting quantum dot coupled to two biased superconducting leads showing a phase difference Φ. Our nonequilibrium transport theory is based on the time evolution of the reduced density matrix obtained by integrating out the fermionic degrees of freedom in the leads. As an example we study a system described as a single-level Anderson impurity model in a two-terminal transistor geometry in the weak coupling regime. Here we investigate the interplay between quasiparticle cotunneling current and phase-driven Cooper-pair tunneling in second order in the tunnel-coupling strength Γ as well as in the limit of large superconducting gaps in the leads.