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TT: Tiefe Temperaturen

TT 22: Transport - Nanoelectronics II: Quantum Dots and Wires, Point Contacts

TT 22.6: Talk

Monday, March 7, 2005, 15:15–15:30, TU H2053

Co-tunneling current and shot noise in quantum dots and molecules — •Axel Thielmann¹, Matthias H. Hettler¹, Jürgen König² und Gerd Schön^1,3 — ¹Forschungszentrum Karlsruhe, Institut für Nanotechnologie,76021 Karlsruhe, Germany — ²Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany — ³Institut für Theoretische Festkörperphysik , Universität Karlsruhe, 76128 Karlsruhe, Germany

We study current and shot noise up to second-order perturbation theory in the coupling of a mesoscopic object (e.g. quantum dot or molecule) to metallic electrodes. In particular, we discuss the influence of co-tunneling processes for the Anderson-impurity model with finite spin splitting. We show that spin-flip co-tunneling leads to a super-Poissonian Fano factor at a different energy scale than expected from first-order calculations. Furthermore, we find the Fano factor in the Coulomb-blockade regime to be very sensitive to the tunnel-coupling strength, which may serve as a spectroscopic tool for the latter.