Photoinduced phase transitions in narrow-gap Mott insulators: the case of VO$_2$

The nonequilibrium dynamics of strongly correlated electrons in photoexcited VO$_2$ is studied using the quantum Boltzmann equation and nonequilibrium Hartree-Fock methods applied to a band structure given by extended density functional theory (DFT+$U$+$V$) and realistic dynamical interactions. The initial equilibration of electrons occurs in hundreds of femtoseconds. For physically reasonable parameters, our Hartree-Fock calculation sustains a new metastable $M_1$ metal phase that is qualitatively consistent with the recent experiment of Morrison et al [1]. The long-term stability of the $M_1$ metal phase will also be considered. [1] V. R. Morrison, R. P. Chatelain, K. L. Tiwari, A. Hendaoui, A. Bruh\'acs, M. Chaker, and B. J. Siwick, Science 346, 445 (2014).