Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 50: Time-resolved spectroscopy II
O 50.4: Vortrag
Freitag, 31. März 2006, 12:00–12:15, WIL C207
Ultrafast dynamics on the Gd(001) surface studied with time-resolved photoelectron spectroscopy — •Panagiotis Loukakos, Martin Lisowski, Uwe Bovensiepen, and Martin Wolf — Fachbereich Physik, Freie Universität Berlin
The Gd(001) surface is an interesting system to study the recently discovered coherent phonon-magnon mode as observed with magneto-optical experiments.1 We use time-resolved photoelectron (TRPE) spectroscopy to analyze directly the dynamical evolution of the electron distribution, after excitation with 1.5 eV, 50 fs laser pulses. The dynamics of the excited system is probed by photoemission with a 6 eV, 80 fs laser pulse. Under normal emission we observe at T=30 K an exchange-split 5dz2 surface state (SS) whose majority component lies 200 meV below the Fermi level. We present the ultrafast dynamics of the occupied SS and distinguish two different fluence and time regimes. At early times where the electron population is far from equilibrium and for low absorbed fluences (<0.1 mJ/cm2) the SS shifts away from the vacuum level. At later time delays, as the electron system thermalizes, the SS shifts towards the vacuum level with dynamics governed by electron-lattice energy transfer. At higher fluences (~1 mJ/cm2) the SS shifts at all times towards the vacuum level. Also, an oscillatory behavior of the occupied SS with a period of 300 fs and an amplitude of only 1 meV is well resolved and observed for the first time in PE spectroscopy. This oscillation period is in excellent agreement with the one observed in optical experiments thereby corroborating the mechanism suggested in Ref. 1.
1. Melnikov et al. Phys. Rev. Lett. 91, 227403 (2003)