Ultrafast disordering of vanadium dimers in photoexcited VO 2
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 the role of disorder. Although ultrafast diffraction provides insights into atomic dynamics during such transformations, diffraction alone probes an averaged unit cell and is less sensitive to randomness in the transition pathway. Using total scattering of femtosecond x-ray pulses, we show that atomic disordering in photoexcited vanadium dioxide (VO2) is central to the transition mechanism and that, after photoexcitation, the system explores a large volume of phase space on a time scale comparable to that of a single phonon oscillation. These results overturn the current understanding of an archetypal ultrafast phase transition and provide new microscopic insights into rapid evolution toward equilibrium in photoexcited matter.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); SLAC National Accelerator Lab., Menlo Park, CA (United States); Duke Univ., Durham, NC (United States); Barcelona Inst. of Science and Technology (Spain); Japan Synchrotron Radiation Research Inst., Hyogo (Japan)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); Ministry of Economy and Business (MINECO) (Spain); Ramón y Cajal programme (Spain); European Regional Development Fund (ERDF); European Union (EU); Japan Synchrotron Radiation Research Inst. (JASRI)
- Grant/Contract Number:
- AC02-76SF00515; SC0016166; AC02-05CH11231; AC05-00OR22725; SEV-2015-0522; RYC-2013-14838; FIS2015-67898-P; 758461; 2016A8008
- OSTI ID:
- 1480375
- Alternate ID(s):
- OSTI ID: 1481692; OSTI ID: 1490850; OSTI ID: 1508593
- Journal Information:
- Science, Journal Name: Science Vol. 362 Journal Issue: 6414; ISSN 0036-8075
- Publisher:
- American Association for the Advancement of Science (AAAS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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