Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

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

TT 47.9: Talk

Thursday, March 17, 2011, 12:45–13:00, HSZ 304

Nonequilibrium Zeeman-splitting in quantum transport through nanoscale junctions — •Sebastian Schmitt and Frithjof B. Anders — Theoretische Physik II, Technische Universität Dortmund

We study an interacting quantum dot –modeled by a single impurity Anderson model– coupled to two different leads where a finite bias voltage is applied. The quantum transport through such a device is governed by the charging energy U of the dot. We employ the scattering-states numerical renormalization-group approach to open quantum systems to study nonequilibrium Green functions and current-voltage characteristics of such a junction. At intermediate to large values of U considerable voltage-dependent redistribution of spectral weight occurs. In a finite magnetic field the Zeeman-split Kondo resonance is rapidly destroyed upon increasing the bias voltage. The nonlinear differential conductance of a particle-hole symmetric as well as particle-hole asymmetric quantum dot is studied for various coupling asymmetries. In contrast to maxima derived from charge-excitations of the quantum dot, the position of the Zeeman-split zero-bias anomaly is independent of these asymmetries. Additionally, at large magnetic fields its position can even exceed the value given by the Zeeman-energy. The results are discussed in connection with recent experiments where similar behavior was encountered.