Photo-induced Mott metal-insulator transition and oscillation in VO$_{2}$

Since Mott predicted the abrupt first-order metal-insulator transition (MIT) in 1949, one of the most important issues in contemporary solid-state physics has been to experimentally prove Mott's MIT in a strongly correlated system with electron-electron interaction. In particular, in order to reveal the mechanism of the Mott MIT, many physicists have paid attention to a representative paramagnetic insulator, VO$_{2 }$(4$d^{1})$, with an abrupt resistance change near 68$^{\circ}$C. The key issue is whether VO$_{2}$ is a Mott insulator, in which the abrupt MIT is not caused by a structural phase transition (SPT), or a Peierls insulator undergoing the SPT near $T_{SPT}\approx $ 68$^{\circ}$C; this question can be answered when a monoclinic metal (MM) phase is observed. Here we show high frequency electrical oscillation a photo-induced MIT and oscillation controlled by adjusting the illumination of infrared light exposed to the VO$_{2}$ film in a two-terminal device. The photo-induced MIT is controlled by the intensity of the light and an applying voltage. The oscillations occur in the MM phase of VO$_{2}$. The oscillations possibly are generated from a temporal capacitor, which is comprised of both temporary dielectric components, arising from inhomogeneity in a VO$_{2}$ film, and MM phases acting like electrodes. This work concludes that the electrical and the optical oscillations are a characteristic of the Mott MIT.