Ultrafast Pump-Probe Studies of the Light-Induced MIT and Recovery of Niobium Dioxide Thin Films

Niobium dioxide (NbO$_{\mathrm{2}})$ is a highly correlated binary oxide that, like vanadium dioxide (VO$_{\mathrm{2}})$, exhibits a first-order insulator-to-metal transition (IMT) at a material-dependent critical temperature, accompanied by a structural transformation from monoclinic to rutile. The nature of the IMT in VO$_{\mathrm{2}}$ has been discussed at length, while fewer studies have been carried out on NbO$_{\mathrm{2}}$. Previous studies show that the IMT can also be optically induced in VO$_{\mathrm{2}}$ on a sub-picosecond timescale; here, we present the first ultrafast pump-probe studies showing this optically-induced transition in NbO$_{\mathrm{2}}$ thin films and compare these results to similar ones carried out on VO$_{\mathrm{2}}$ thin films.