Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 44: Transport: Nanoelectronics III - Molecular Electronics 2
TT 44.3: Vortrag
Donnerstag, 29. März 2012, 15:30–15:45, BH 334
Spin transport and tunable Gilbert damping in a single-molecule magnet — •Milena Filipovic1, Federica Haupt2, Cecilia Holmqvist1, and Wolfgang Belzig1 — 1Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany — 2Institut für Theorie der Statistischen Physik, RWTH Aachen, D-52056 Aachen, Germany
We study spin transport through a molecular level coupled
to two leads and a single-molecule magnet in a magnetic
field. The molecular spin is treated as a classical variable and, due to the external magnetic field, precesses around the field axis.
Expressions for charge and spin currents are derived by
means of the Keldysh nonequilibrium Green’s function technique in linear response.
The exchange coupling between the electronic spins and the magnetization dynamics of the molecule creates inelastic tunneling processes which
contribute to the spin currents. The inelastic spin currents, in turn, generate a spin transfer torque [1,2] acting
on the molecular spin. This back-action includes one component that gives a contribution to the Gilbert damping and one
component that changes the precession frequency.
The Gilbert damping coefficient, α, can be controlled by changing the bias and gate voltages, and has a non-monotonic dependence
on the tunneling rates. We compare our results to the Gilbert
damping coefficient calculated in Ref. [3] in the small precession frequency regime ℏω≪ kBT.
Y. Tserkovnyak et al., Rev. Mod. Phys. 77, 1375 (2005).
C. Holmqvist et al., Phys. Rev. B 83, 104521 (2011).
N. Bode et al., arXiv:1110.4270v1 (2011).