Raman spectra and elastic light scattering dynamics of V3O5 across insulator–metal transition

The observation of Raman-active mode softening is a powerful tool to understand phase transition mechanisms in solids. The evolution of the phonon spectrum of technologically important correlated oxide V 3O 5 attracts much attention for the steady-state regime and for ultrashort temporal scales since thermal contribution to the insulator-to-metal (IMT) transition is excluded during the first few picoseconds. Here, we show theoretical modeling of V 3O 5 phonon spectrum and experiment. It is shown that the IMT is a first-order phase transition. Photoinduced transition was observed by a elastic light scattering technique, showing the principal difference in V 3O 5 surface dynamics across IMT for thermally and ultrafast light-induced phase transitions. The ultrafast IMT is accompanied primarily by short-range optical phonon interactions with a negligible contribution by acoustic phonons, while the acoustic phonons provide a key contribution to the transformation of surface geometry upon thermally induced IMT. Scattering imaging of surface autocorrelation function upon IMT shows the rise of optical homogeneity in the lateral direction of the surface in the steady-state regime and on a subpicosecond time scale.