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. This study investigates the photoinduced phase transformation of Rb_0.94Mn_0.94Co_0.06[Fe(CN)₆]_0.98, exhibiting a 75 K thermal hysteresis around room temperature. A novel streaming powder sample technique monitors structural changes via ultrafast X-ray diffraction. The photoinduced polarons expand the lattice, and the tetragonal-to-cubic transition occurs within 100 ps above a threshold fluence. This is explained using Landau theory as an elastically driven, cooperative process. The streaming technique is applicable to studying other ultrafast, non-reversible dynamics.

Marius Hervé, Gaël Privault, Elzbieta Trzop, Shintaro Akagi, Yves Watier, Serhane Zerdane, Ievgeniia Chaban, Ricardo G. Torres Ramírez, Celine Mariette, Alix Volte, Marco Cammarata, Matteo Levantino, Hiroko Tokoro, Shin-ichi Ohkoshi, Eric Collet