Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Transport: Poster Session

TT 22.3: Poster

Mittwoch, 27. Februar 2008, 14:00–18:00, Poster B

Influence of spin waves on transport through a quantum-dot spin valve — •Björn Sothmann¹, Jürgen König¹, and Anatoli Kadigrobov^1,2 — ¹Theoretische Physik III, Ruhr-Universität Bochum, D-44780 Bochum — ²Department of Physics, Göteborg University, SE-412 96 Göteborg

We study transport through a quantum-dot spin valve, i.e. a single-level quantum dot with strong Coulomb interaction tunnel coupled to ferromagnetic leads with non-collinear magnetizations. By applying a bias voltage, a spin on the dot is created, reducing the conductance. Furthermore, there is an exchange field due to the Coloumb interaction. In the case of linear transport this leads to a decrease of the spin valve effect, while in the case of nonlinear transport it gives rise to a negative differential conductance.

In Ref. [1] a real-time diagrammatic technique was developed to describe transport through quantum dot spin valves. We generalize this theory to include the excitation of spin waves in the leads. Thereby we distinguish the regimes of the spin wave energy being comparable or being much larger than the tunnel coupling. By solving a generalized master equation for the system’s reduced density matrix, we derive the transport properties of the system in the different regimes in linear and non-linear response.

[1] M. Braun, J. König, J. Martinek, Phys. Rev. B 70, 195345 (2004).