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1 March 2010Ultrafast coherent control of electric currents at metal surfaces
We report the development of an experimental technique to measure the dynamics of electrical currents on
the femtosecond timescale. The technique combines methods of coherent control with time- and angle-resolved
photoelectron spectroscopy. Direct snapshots of the momentum distribution of the excited electrons as function
of time are then determined by photoelectron spectroscopy. In this way we gain information on the generation and
decay of ultrashort current pulses in unprecedented detail. In particular, this technique allows the observation
of elastic electron scattering in terms of an incoherent population dynamics in momentum space. We have
applied this optical current generation and detection scheme to electrons in so-called image-potential states
which represent a prototype of two-dimensional electronic surface states. Electrons in these states are bound
perpendicular to the metal surface by the Coulombic image potential whereas they can move almost freely parallel
to the surface. For the (n=1) image-potential state of Cu(100) we find a decay time of 10 fs due to electron
scattering with steps and surface defects.
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Jens Güdde, Marcus Rohleder, Torsten Meier, Stephan W. Koch, Ulrich Höfer, "Ultrafast coherent control of electric currents at metal surfaces," Proc. SPIE 7600, Ultrafast Phenomena in Semiconductors and Nanostructure Materials XIV, 76001K (1 March 2010); https://doi.org/10.1117/12.839672