We are interested in the spatio-temporal response of nanostructures and molecules at surfaces following ultrafast laser excitation.
Our goal is to obtain an atomistic understanding of such photoinduced processes on (sub-)nanometer length and femtosecond time scales
by employing pump-probe schemes for ultrafast scanning probe microscopy (SPM).
Ultrafast excitation of matter to a non-equilibrium state can launch a variety of excited state dynamics and relaxation processes,
providing insight into microscopic properties and fundamental physical mechanisms. In nanostructures, molecules and spatially
inhomogeneous systems, the dynamics will be dictated by the local environment, and will spatially vary on nanometer or even Angstrom
length scales. With pump-probe SPM, we envision to study the dynamics of charge carriers, quasiparticles and local transient changes
of the electronic and geometric structure directly on atomic length scales. Ultimately, pump-probe SPM allows for probing the dynamics
of individual molecules directly in the time domain.
The figure sketches the concept of a THz-gated STM. Coupling THz-pulses to a scanning tunneling microscope tip allows for driving
tunneling currents within an ultrashort time window, maintaining the spatial resolution of the STM.