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Prof. Dr. Martin Wolf
Abt. Physikalische Chemie
Fritz-Haber Institut der MPG
Faradayweg 4-6
14195 Berlin, Germany
phone:+49 30 8413-5111
Fax: +49 30 8413-5106

hitherto (2010):
Department of Physics
Free University Berlin
Arnimallee 14
D - 14195 Berlin


Coherent Optical Phonons and Parametrically Coupled Magnons Induced by Femtosecond Laser Excitation of the Gd(0001) Surface 

The above animation depicts the experiment and the investigated phenomenon on the Gadolinium surface schematically. The pump-laser pulse is absorbed near the surface and excites electrons, a process that happens instantly on the investigated time scale. Due to the special character of the exchange split surface state, a quasi Coulomb force drives the surface layer away from the bulk part. That force recedes after the electronic lifetime of the surface state components (about 10fs). Subsequently, the surface layer relaxes by lattice vibrations with a period of 330fs (top panel at right). The magnetization of the surface is measured in parallel (lower panel at right). It follows the vibration of the surface layer because the interaction which aligns the elementary magnetic moments (exchange interaction) is determined by the overlap of the surface and subsurface layer, which changes during the vibration. Thus, the oscillations in the surface magnetization (Msurf) occurs at the same frequency as the vibrations of neighboring atoms. Note that damping of these vibrations is governed by the excited electron distribution (color code of Gd atoms), which developed after electrons relaxed in the surface state. The excited electron distribution differs from the one of the ground state and therefore changes the ion potential along the surface normal. As soon as the electronic distribution has cooled to the equilibrium value (i.e. nonexcited state), the amplitude has vanished.

Restart the movie.

Phys. Rev. Lett.;
press release of the Freie Universitšt Berlin

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