Three-particle approximation for transition-metal oxides

Quasiparticle spectra are calculated for NiO and CuO on the basis of band structures obtained within the ab initio self-interaction-corrected local-spin density (SIC-LSD) and LSD+U approximations. On-site Coulomb correlations are described by a multiband Hubbard model, which is treated within Igarashi's three-particle approximation. The transition-metal d-state spectral weight is split into a main ${\mathrm{d}}^{\mathrm{n}}$L peak and a ${\mathrm{d}}^{\mathrm{n}\mathrm{-}1}$ satellite. We show that mean-field band structures in this way can lead to a good description of the experimental photoemission spectra of these compounds. The validity of the three-particle approach is investigated, and it is concluded that the method is best suited for a system which is well orbitally polarized on the mean-field level.