Studying condensed matter far from equilibrium

We use ultrashort laser pulses in optical pump-probe experiments to study the photoinduced dynamics in amorphous and crystalline nanostructured materials. In these types of experiments, the action of the pump pulse is analysed by comparing the modifications of the probe pulse characteristics, e.g. transmitted intensity, before and at various time delays with respect to the pump. The time resolution in these experiments is thus only limited by the temporal cross-correlation of the pump and probe pulse. It therefore allows insight into sub-picosecond coupling between electron and lattice system far from equilibrium.

In addition, we investigate properties of materials in non-equilibrium states in electrical experiments. For this purpose, we fabricate nanostructured devices that allow us to quench a material’s atomic configuration to a disordered glass state and subsequently measure its electronic properties. The atomic structure of the glass continuously evolves in time, as made apparent by measuring the likewise evolving electronic properties. Here, one of the experimental challenges lies in broad characteristic timescale of structural processes. Following the entire history of a sample requires accurate measurements on the nanosecond timescale of the quenching process, as well as measurement protocols that can uncover the temperature activated structural dynamics on a timescale from microseconds to days. Accurate models of the structural dynamics should open up new applications for these materials in electronic devices.

 

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