Ultrafast disordering of vanadium dimers in photoexcited VO 2

• DOI: 10.1126/science.aau3873
• Publication Date: 2018-11-01T18:04:41Z
• Authors: Simon Wall; Shan Yang; Luciana Vidas; Matthieu Chollet; James M. Glownia; Michael Kozina; Tetsuo Katayama; Thomas Henighan; Mason Jiang; Timothy A. Miller; David A. Reis; Lynn A. Boatner; Olivier Delaire; Mariano Trigo
• Keywords: Photoexcitation; Ultrafast electron diffraction; Oscillation (cell signaling)

Many ultrafast solid phase transitions are treated as chemical reactions that transform the structures between two different unit cells along a reaction coordinate, but this neglects role of disorder. Although diffraction provides insights into atomic dynamics during such transformations, alone probes an averaged cell and is less sensitive to randomness in transition pathway. Using total scattering femtosecond x-ray pulses, we show disordering photoexcited vanadium dioxide (VO2) central mechanism that, after photoexcitation, system explores large volume space on time scale comparable single phonon oscillation. These results overturn current understanding archetypal provide new microscopic rapid evolution toward equilibrium matter.