Fig. 3: Simulations of the ultrafast phase transition.
From: Decoupled few-femtosecond phase transitions in vanadium dioxide
a TN-MF simulated optical conductivity before and 13 fs after photoexcitation showing instantaneous bandgap collapse. b Illustration of the two components of the structural distortion. c Structural dynamics following the phase transition. The dimerization relaxes prior to the tilt, overshooting the rutile positions, before fully relaxing in less than 100 fs. d DOS calculated with DFT for the monoclinic and rutile phases, and for a structural configuration (M0) close to that predicted by the TN-MF calculations for ~20 fs delay. e Ratio of the DOS of the M0 configuration and the rutile phase. The DOS near the Fermi level in the M0 phase exhibits several minima as compared to the rutile phase. Electrons generated at energies excited by the pump (red Gaussian in d) need to relax across these minima prior to full thermalization.
