Chemical bonding and many-body effects in site-specific x-ray photoelectron spectra of corundum ${\mathrm{V}}_2{\mathrm{O}}_3$

Site-specific x-ray photoelectron spectroscopy together with density functional theory calculations based on the local density approximation have identified the chemical bonding, single-particle matrix element, and many-body effects in the x-ray photoelectron spectrum of corundum ${\mathrm{V}}_2{\mathrm{O}}_3$. Significant covalent bonding in both the upper and lower lobes of the photoelectron spectrum is found, despite the localized nature of the $\mathrm{V}3d$ electrons that are responsible for the Mott behavior. We show that the approximate treatment of correlation dominates the discrepancy between theory and experiment in the near-Fermi-edge region and that many-body effects of the photoemission process can be modeled by Doniach-Šunjić [J. Phys. C 3, 285 (1970)] asymmetric loss. Correlation effects govern the relative intensity and energy position of the higher level electron bands, and many-body effects dominate the “tail” region of both the upper and lower lobes of the photoemission spectrum.

Figure 1

Experimental valence-photoelectron spectra $(h\nu \approx 2286\mathrm{eV})$, theoretical density of states curves (DOS), theoretical density of states curves corrected for individual angular-momentum dependent photoelectron cross sections (c-DOS), and theoretical density of states curves corrected for both individual angular-momentum dependent photoelectron cross sections and the Doniach-Šunjić effect (cc-DOS) for (a) V, (b) O, and (c) total spectrum. $\mathrm{p}$ indicates partial DOS. (a) and (b) additionally show partial angular-momentum-resolved DOS curves for $\mathrm{V}3d$, $\mathrm{V}4s$, and $\mathrm{V}4p$, and $\mathrm{O}2s$ and $\mathrm{O}2p$, respectively. Curves have been scaled to equal peak heights.

Figure 2

High-resolution photoelectron spectrum of the near-Fermi region $(h\nu \approx 2286\mathrm{eV})$, compared to the theoretical density of states in that region. Experimental valence-photoelectron spectrum (top), theoretical density of states curve corrected for individual angular-momentum dependent photoelectron cross sections (c-DOS) (bottom), and theoretical density of states curve corrected for both individual angular-momentum dependent photoelectron cross sections and the Doniach-Šunjić effect (cc-DOS) (middle). Curves have been scaled to equal peak heights.

Figure 3

Comparison of the $2p_{3∕2}$ core level and the valence-band photoemission spectra for (a) ${\mathrm{V}}_2{\mathrm{O}}_3$ $(h\nu \approx 2286\mathrm{eV})$ and (b) $\mathrm{Ti}{\mathrm{O}}_2$ $(h\nu \approx 2695\mathrm{eV})$. Curves have been scaled to equal peak heights and shifted in binding energy.