Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 35: Postersession Transport: Nanoelectronics, Quantum Coherence and Quantum Information, Fluctuations and Noise
TT 35.3: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Influence of spin waves on transport through a quantum-dot spin valve — •Björn Sothmann1,2, Jürgen König1,2, and Anatoli Kadigrobov3,2 — 1Theoretische Physik, Universität Duisburg-Essen, Germany — 2Theoretische Physik III, Ruhr-Universität Bochum, Germany — 3Departement of Physics, Göteborg University, Sweden
A quantum-dot spin valve, i.e. a single-level quantum coupled to ferromagnetic leads with arbitrarily oriented magnetizations, reveals interesting transport properties as e.g. negative differential conductance due to an interplay between non-equilibrium spin accumulation on the quantum dot and spin precession due to an exchange field which is created by virtual tunneling to the leads.
In order to describe the influence of spin waves on transport through a quantum-dot spin valve, we generalize the real-time diagrammatic transport theory developed in Ref. [1] to include magnonic degrees of freedom in the leads. In the regime of large spin-wave energies, we find that the formation of a trapping state leads to a negative differential conductance. Moreover, we find that magnons will be pumped from the source to the drain lead. In addition, we observe that the magnons can pump a completely spin-polarized current at zero bias voltage. We also report on the zero- and finite-frequency current noise. We find the latter to be sensitive to the magnonic contributions to the exchange field.
[1] M. Braun, J. König, J. Martinek, Phys. Rev. B 70, 195345 (2004).
[2] B. Sothmann, J. König, A. Kadigrobov, in preparation.