Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 30: Focus Session "Spin Currents in Magnetic Nanostructures", Organization: Mathias Kläui (Univ. Mainz)
MA 30.8: Vortrag
Mittwoch, 28. März 2012, 18:00–18:15, EB 301
Wave-diffusion theory of spin transport in metals after ultrashort-pulse excitation — •Steffen Kaltenborn1, Yao-Hui Zhu2, and Hans Christian Schneider1 — 1University of Kaiserslautern, Kaiserslautern, Germany — 2Beijing Technology and Business University, Beijing, China
We present theoretical results for spin and charge-current dynamics after ultrafast spin-polarized excitation in a normal metal. It is first shown analytically how the macroscopic wave-diffusion equations [1] provide a unified description of ballistic and diffusive properties of spin and charge transport including the "intermediate" regime in which transport is characterized by both ballistic and diffusive features. These equations are then applied to a simplified model of ultrafast excitation of spin polarized carriers in gold films of thickness up to several hundred nanometers. If one assumes spin-dependent momentum relaxation times, the computed dynamics of the spin and charge density at the surface of the films of varying thickness qualitatively reproduce recent measurements [2], which were interpreted as arising from the transition from ballistic to diffusive transport. Our calculations support this interpretation, and indicate that the signatures observed in the experiment are quite generic for ultrashort timescales and thin films because they can be traced back to a combination of ballistic and diffusive properties of spin and charge transport.
[1] Y.-H. Zhu, B. Hillebrands, and H. C. Schneider, Phys. Rev. B 78, 054429 (2008)
[2] A. Melnikov et al., Phys. Rev. Lett. 107, 076601 (2011)