Ultrafast and persistent photoinduced phase transition at room temperature monitored by streaming powder diffraction.

Hervé, Marius; Privault, Gaël; Trzop, Elzbieta; Akagi, Shintaro; Watier, Yves; Zerdane, Serhane; Chaban, Ievgeniia; Torres Ramírez, Ricardo G et al. · Nat Commun · 2024

basic_science · Level V

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Abstract

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. Time-resolved studies provide fundamental mechanistic insight into far-from-equilibrium electronic and structural dynamics. Here we study the photoinduced phase transformation of the Rb<sub>0.94</sub>Mn<sub>0.94</sub>Co<sub>0.06</sub>[Fe(CN)<sub>6</sub>]<sub>0.98</sub> material, designed to exhibit a 75 K wide thermal hysteresis around room temperature between Mn<sup>III</sup>Fe<sup>II</sup> tetragonal and Mn<sup>II</sup>Fe<sup>III</sup> 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 the photoinduced polarons expand the lattice, while the tetragonal-to-cubic photoinduced phase transition 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 the streaming powder technique to study non-reversible and ultrafast dynamics.