Fig. 4: Bandgap evolution as a function of excited electron percentage.
From: Photoinduced hidden monoclinic metallic phase of VO2 driven by local nucleation

The band gap of the VO2 at 50 fs following the photoexcitation as a function of the percentage of excited valence electrons in comparison with that narrowed by the electron correlation effect at the same photoexcitation but frozen the atomic structure to the M1 phase.