Low-energy excitations in strongly correlated materials: A theoretical and experimental study of the dynamic structure factor in V₂O₃

This work contains an experimental and theoretical study of the dynamic structure factor at large momentum transfer Q∼4 ^-1 of the strongly correlated transition-metal oxide V₂O₃. We focus in particular on the transitions between d states that give rise to the spectra below 6 eV. We show that the main peak in this energy range is mainly due to t_2g→egσ transitions, and that it carries a signature of the phase transition between the paramagnetic insulator and the paramagnetic metal that can already be understood from the joint density of states calculated at the level of the static local density approximation. Instead, in order to obtain theoretical spectra that are overall similar to the measured ones, we have to go beyond the static approximation and include at least crystal local field effects. The latter turn out to be crucial in order to eliminate a spurious peak and hence allow a safe comparison between theory and experiment, including an analysis of the strong anisotropy of the spectra.