Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 21: Transport: Nanoelectronics II - Spintronics and Magnetotransport - Part 2
TT 21.5: Vortrag
Dienstag, 28. März 2006, 17:15–17:30, HSZ 105
Sequential and Co-Tunneling Shot Noise in Quantum Dot Spin Valves — •Matthias Hettler1, Axel Thielmann1, Jürgen König2, and Gerd Schön1,3 — 1Forschungszentrum Karlsruhe, Institut für Nanotechnologie — 2Institut für Theoretische Physik III, Ruhr-Universität Bochum — 3Institut für Theoretische Festkörperphysik, Universität Karlsruhe
For a single level quantum dot coupled to ferromagnetic electrodes transport is sensitively dependent on the magnetic orientation and degree of polarization of the electrodes. If in addition a magnetic field leads to Zeemann split states on the quantum dot, the additional energy scale of inelastic co-tunneling processes comes into play. Co-tunneling processes strongly influence the transport not only in the Coulomb-blockade regime, but also around the resonances and above the sequential tunneling threshold, even at quite small dot-electrode coupling. In particular, the shot noise displays rich behavior that can only be understood by dealing with sequential and co-tunneling processes on equal footing. We present a diagrammatic approach to this problem that is valid for for arbitrary Coulomb interaction and accounts for non-Markovian memory effects relevant to the shot noise [1]. We observe spin-accumulation and spin-inversion on the quantum dot and predict strongly non-monotonic behavior of the shot noise with peaks and peak-dip features as well as various regimes where the noise is anomalously enhanced (super-Poissonian noise).
[1] A. Thielmann, M. H. Hettler, J. König, and G. Schön, Phys. Rev. Lett. 95, 146806 (2005).