Ernest Pastor, who holds a CNRS Junior Professor Chair at IPR, has helped showing that the Born-Oppenheimer approximation must be overcome to account for the ultrafast transformations of a crystal illuminated by a laser flash.
By studying vanadium dioxide VO2, a material that undergoes an ultra-rapid modification of its crystal structure when illuminated by a laser flash, the researchers highlighted the unexpected role of non-adiabatic forces. Their observations consisted of a very close sequence of ultra-fast X-ray diffraction measurements of a VO2 crystal, carried out at the SACLA accelerator in Japan. In this way, they were able to create a complete "movie" of the material's transformation on an atomic scale, following its excitation by the laser flash.
Ultrafast lattice disordering can be accelerated by electronic collisional forces, de la Peña Muñoz, G.A., Correa, A.A., Yang, S., Delaire, O., Huang, Y., Johnson A.S., Katayama, T., Krapivin, V., Pastor, E., Reis, D.A., Teitelbaum, S., Vida, L., Wall, S. et Trigo, M, Nature Physics, publié le 29 juin 2023