Ultrafast and persistent photoinduced phase transition at room temperature monitored by streaming powder diffraction
Résumé
Ultrafast photoinduced phase transitions at room temperature, driven by a single laser shot and persisting long after stimuli, represent emerging routes for ultrafast control over materials' properties. Timeresolved studies provide fundamental mechanistic insight into far from equilibrium electronic and structural dynamics. Here we study the photoinduced phase transformation of the Rb0.94Mn0.94Co0.06[Fe(CN)6]0.98 material, designed to exhibit a 75 K wide thermal hysteresis around room temperature between Mn III Fe II tetragonal and Mn II Fe III cubic phases. We developed a specific powder sample streaming technique to monitor by ultrafast X-ray diffraction the structural and symmetry changes. We show that photoinduced polarons expand lattice, while the tetragonal to cubic PIPT occurs within 100 ps above threshold fluence. These results are rationalized within the framework of the Landau theory of phase transition as an elastically-driven and cooperative process. We foresee broad applications of streaming powder technique to study non-reversible and ultrafast dynamics.
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