Time-Resolved Investigation of Coherently Controlled Electric Currents at a Metal Surface
J. Güdde,
M. Rohleder,
T. Meier,*
S. W. Koch,
U. Höfer
Studies of current dynamics in solids have been hindered by
insufficiently brief trigger signals and electronic detection
speeds. By combining a coherent control scheme with photoelectron
spectroscopy, we generated and detected lateral electron currents
at a metal surface on a femtosecond time scale with a contact-free
experimental setup. We used coherent optical excitation at the
light frequencies
a and
a/2 to induce the current, whose direction
was controlled by the relative phase between the phase-locked
laser excitation pulses. Time- and angle-resolved photoelectron
spectroscopy afforded a direct image of the momentum distribution
of the excited electrons as a function of time. For the first
(
n = 1) image-potential state of Cu(100), we found a decay time
of 10 femtoseconds, attributable to electron scattering with
steps and surface defects.
* Present address: Department Physik, Universität Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany.
To whom correspondence should be addressed. E-mail: hoefer{at}physik.uni-marburg.de
