Daniel Becker, Stephan Weiss, Michael Thorwart, Daniela Pfannkuche
We study the nonequilibrium dynamics of a spinful single-orbital quantum dot with an incorporated quantum mechanical spin-1/2 magnetic impurity. Due to the spin degeneracy, double occupancy is allowed and Coulomb interaction together with the exchange coupling of the magnetic impurity influence the dynamics. We employ the iterative summation of real time path integrals (ISPI) to obtain the time-dependent nonequilibrium tunneling current through the system and the real-time impurity polarisation. By monitoring observables as a function of the propagation time, we are able to determine characteristics of the time-dependent nonequilibrium dynamics. Upon further extending the established ISPI method to this coupled system, we investigate the relaxation dynamics of the impurity under the influence of a nonequilibrium current. Likewise, the back action of the impurity on the charge current is addressed on the same footing. Especially in the deep quantum regime, when all time- and energy scales are of the same order of magnitude, the ISPI method allows us to obtain accurate results for the magnetic Anderson quantum dot under nonequilibrium conditions. In particular, no perturbative approach is applicable in this regime of parameters.
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http://arxiv.org/abs/1205.2462
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