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TT: Fachverband Tiefe Temperaturen

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

TT 47.8: Vortrag

Donnerstag, 17. März 2011, 12:30–12:45, HSZ 304

Transport through quantum-dot spin valves with a magnetic impurity — •Björn Sothmann and Jürgen König — Theoretische Physik, Universität Duisburg-Essen

Quantum-dot spin valves, i.e., quantum dots coupled to ferromagnetic electrodes with noncollinear magnetizations exhibit a number of interesting effects. On the one hand, spin accumulates on the dot and blocks further transport. On the other hand, an effective exchange field gives rise to a precession of the accumulated spin thereby lifting the spin blockade [1].

Here, we investigate transport through a quantum-dot spin valve with a side-coupled spin on the dot using a real-time diagrammatic approach. We find that for a large external magnetic field, the current is insensitive to the coherent dynamcis of the two spins on the dot. In contrast, the finite-frequency noise acquires a peak at the precession frequency of the spins. For a small magnetic field, the system exhibits a nontrivial spin dynamics due to the interplay between exchange coupling, external magnetic field and exchange field. We show how this spin dynamics can be studied in the finite-frequency noise.
M. Braun, J. König, J. Martinek, Phys. Rev. B 70, 195345 (2004).
B. Sothmann, J. König, arXiv:1009.5901, Phys. Rev. B in press.