title: Ultrafast electron crystallography of the cooperative reaction path in vanadium dioxide.
abstract: Time-resolved electron diffraction with atomic-scale spatial and temporal resolution was used to unravel the transformation pathway in the photoinduced structural phase transition of vanadium dioxide. Results from bulk crystals and single-crystalline thin-films reveal a common, stepwise mechanism: First, there is a femtosecond V-V bond dilation within 300 fs, second, an intracell adjustment in picoseconds and, third, a nanoscale shear motion within tens of picoseconds. Experiments at different ambient temperatures and pump laser fluences reveal a temperature-dependent excitation threshold required to trigger the transitional reaction path of the atomic motions.
authors.affiliation: Department of Chemistry, University of Houston , Houston, Texas 77204, USA.
authors.forename: Ding-Shyue
authors.initials: DS
authors.lastname: Yang
authors.affiliation: Ludwig-Maximilians-Universität München , Am Coulombwall 1, 85748 Garching, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Baum
authors.affiliation: Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology , Pasadena, California 91125, USA.
authors.forename: Ahmed H
authors.initials: AH
authors.lastname: Zewail