•W. Pfeiffer1, S. Dantscher1, C. Kennerknecht1,
S. Schramm1, H.B. Weber2 und J.U. Würfel2
1Physikalisches Institut EP1, Universität Würzburg,
97074 Würzburg
2Forschungszentrum Karlsruhe, Institut für Nanotechnologie,
D-76021 Karlsruhe
Microscopic break junctions provide fascinating possibilities to investigate
microscopic charge transport phenomena. Up to now the studies are restricted
to DC current measurements. Consequently, the illumination of the contact
and the investigation of the resulting photocurrents opens a new field
of research. Especially, ultrashort laser pulses combined with time-resolved
spectroscopy could then reveal details of the charge transfer dynamics
that are of utmost importance for the understanding of the conductivity
in nanoscale contacts. We present first experiments on the illumination
of tunnel junctions and single molecule contacts with ultrashort laser
pulses (800 nm and 400 nm, 50 fs). The junctions are stable up to intensities
of 108 W cm-2 and thus allow the investigation of
microscopic transport in intense laser fields. The mechanisms leading to
a light induced modulation of the conductance are discussed for tunnel
junctions and single molecule contacts.