Maurizio Monti
Institut des Molécules et des Matériaux du Mans
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Understanding the ultrafast dynamics of complex materials
Abstract: Studying the dynamical behaviour of materials is essential to pave the way for the possibility of controlling material functionality on an ultrafast time scale. Often, however, the material response is the result of the competition between the different degrees of freedom present in the system (electronic, vibrational, structural…) which complicates the analysis and interpretation of experiments.By applying a variety of techniques, it is possible to disentangle the problem by separate the material response through different energy ranges and timescales.This seminar will present how such a multimessenger approach makes it possible to distinguish different physical mechanisms, and resolve contradictory or unexpected results. The first part will focus on the dynamics of hot carriers in perovskite semiconductors, where a combination of visible and terahertz spectroscopy techniques was employed to unambiguously determine the hot carrier cooling time, and consequently gather insight on the strength of electron-phonon and phonon-phonon coupling. The second part will present the application of time-resolved surface x-ray scattering on a prototypical manganite, which allowed to isolate the surface dynamics from the bulk during a laser-induced phase transition. By separating these two components, it was possible to determine the origin of the ambiguous response of the bulk Bragg peak, by showing that melting happens preferentially at the surface.
