A high-repetition-rate pump-probe experiment is presented, based on the asynchronous sampling approach. The low-α mode at the synchrotron ANKA can be used for a time resolution down to the picosecond limit for the time-domain sampling of the coherent THz emission as well as for hard X-ray pump-probe experiments, which probe structural dynamics in the condensed phase. It is shown that a synchronization of better than 1 ps is achieved, and examples of phonon dynamics of semiconductors are presented.
We investigated the lattice dynamics of the prototypic ferroelectric barium titanate close to its ferroelectric--paraelectric phase transition aiming at a better understanding of the atomistic nature of the transition. The usage of time-resolved X-ray techniques allows to disentangle lattice motion and unit cell changes, which, in part, relate to the ferroelectric polarization. In the quasi-static case both the electrical and the laser excitation show a mean-field, simple thermal behaviour, while for time scales shorter than nanoseconds the impulsive nature of the excitation becomes visible.
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