Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 4: Transport: Quantum Dots, Quantum Wires, Point Contacts I (TT jointly with O)
O 4.6: Vortrag
Montag, 31. März 2014, 10:45–11:00, BEY 81
Non-equilibrium transport through a Josephson quantum dot — •Jan Frederik Rentrop1,2, Severin Jakobs1,2, and Volker Meden1,2 — 1Institut für Theorie der Statistischen Physik, RWTH Aachen University, Germany — 2JARA Fundamentals of Future Information Technology, 52056 Aachen, Germany
We investigate a quantum dot featuring Hubbard interaction coupled to superconducting leads. Applying a bias voltage across the system leads to a time-dependent periodic Hamiltonian. This implies that the observable, namely the current through the system, aquires a periodic time-dependence (AC Josephson effect). The non-equilibrium feature of so called Multiple Andreev Reflections (MAR), known from the non-interacting case, is observed in the static component of the current.
The self-energy on the dot is calculated with the functional renormalization group method. The derived first and second order truncation schemes allow for a "quasi-static" (i.e. allowing for the periodic time-dependence but not more) approximation of the self-energy. Model and method allow for asymmetric choices of the super-conducting gaps, the lead temperatures, the lead-dot couplings, tuning of the Hubbard interaction, shifting of on-site energy and applying a magnetic field. Numerical results are presented for symmetric choices at zero magnetic field and zero temperature, while lead-dot coupling, on-site energy and Hubbard interaction are tuned. Also, first order self-consistent perturbation theory results are presented as a benchmark.
We discuss limitations that the MAR physics impose on any perturbative scheme that expands in small orders of the interaction.