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TT: Fachverband Tiefe Temperaturen

TT 47: TR: Nanoelectronics I - Quantum Dots, Wires, Point Contacts 1

TT 47.7: Talk

Thursday, March 17, 2011, 12:15–12:30, HSZ 304

Correlated current- and spin dynamics in a quantum dot with magnetic impurity — •Daniel Becker, Stephan Weiß, Michael Thorwart, and Daniela Pfannkuche — I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg

Based on the numerically exact, non-perturbative scheme of iterative summation of path integrals (ISPI)[1,2], the fully correlated dynamics of a single-level quantum dot is studied, which contains a quantum spin-1/2 magnetic impurity, interacting with the dot-electron spins, and is in contact with unpolarized, metallic leads. The main focus lies on the charge current and electron-induced dynamics of the impurity spin. Their dependence on crucial model parameters, such as the on-dot interaction strengths (Coulomb, electron-impurity), the bias voltage, and the temperature is systematically investigated in the non-perturbative regime, where all appearing energy scales are of the same order of magnitude. Due to flip-flop processes between electron- and impurity spins and stochastic tunneling of electrons onto and off the dot, a polarization of the impurity spin decays exponentially, even for vanishing charge current. The current, in turn, is solely affected by the longitudinal part of the electron-impurity interaction, which acts as an effective magnetic field. From the dependence of the impurity relaxation time on the bias voltage, conclusions about the nontrivial energy level structure can be drawn, while the charge current shows a monotonic dependence on the bias voltage.
S. Weiss et al., Phys. Rev. B 77, 195316 (2008)
D. Becker et al., J. Phys.: Conf. Ser. 245 012021 (2010)