Experimentalphysik / Nanowissenschaften auf ultrakurzen Zeitskalen


Scientific scope

The ground-state properties of complex materials, as well as the reaction pathways of photo-excited states, are governed by many-body phenomena and the mutual dependence of electron, spin and lattice subsystems. Ultrafast techniques provide access to these fundamental correlations as femtosecond light pulses allow for subsystem-specific excitations and time-resolved observation of the same or another subsystem’s response. In the limit of weak optical excitation, this concept may be seen as an experimental perturbative approach where correlations governing ground state properties are revealed by the system’s response to modest, but specific excitations. Employing intense ultrashort laser pulses, on the other hand, allows for the preparation of transient states of matter exhibiting strong non-equilibrium, in particular between electrons and lattice. The coupling of the subsystems of such states can be significantly different compared to the ground state and the induced photo-physical or photo-chemical reaction may follow a non-thermal reaction pathway not available in thermal equilibrium. This experimental concept requires the application of different, complementary probes revealing the temporal evolution of the different subsystems.