Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 25: Zeitaufgelöste Spektroskopie II

O 25.2: Vortrag

Samstag, 5. März 2005, 15:15–15:30, TU EB420

Time Resolved Nonlinear Magneto-Optical Spectroscopy at Gd(0001) Surface: Ultrafast Lattice and Spin Dynamics — •Ilie Radu, Alexey Melnikov, Uwe Bovensiepen, Kai Starke, Eckart Matthias, and Martin Wolf — Freie Universität Berlin, Fachbereich Physik, Arnimmalle 14, 14195 Berlin

Pump-probe second harmonic generation (SHG) measurements performed on ferromagnetic Gd(0001) surfaces revealed the existence of a coupled coherent phonon-magnon mode at frequency of 3 THz [1]. This is reflected in oscillatory contributions in the transient SHG signal for the electron, phonon and spin subsystems. Here, we present the strong wavelength dependence of incoherent and coherent components of the time-resolved SHG response following the excitation with 35 fs laser pulses within 740-860 nm wavelength range. The SHG process at Gd surfaces evolves resonantly enhanced via the unoccupied surface state component which implies a high spectral sensitivity. With increasing photon energy we observe an increase in the incoherent contribution and a decrease in the coherent part of the excitation. This is ascribed to a population build-up in the unoccupied spin down surface state which increases with hν, while the depopulation of the occupied component, occurring simultaneously, varies just weakly with photon energy.

This project is funded by DFG through SPP 1133.

[1] A. Melnikov et al.; Phys. Rev. Lett. 91, 227403 (2003)