Local correlations and hole doping in NiO: A dynamical mean-field study

Using a combination of ab initio band-structure methods and dynamical mean-field theory, we study the single-particle spectrum of the prototypical charge-transfer insulator NiO. Good agreement with photoemission and inverse-photoemission spectra is obtained for both stoichiometric and hole-doped systems. In spite of a large $\mathrm{Ni}d$ spectral weight at the top of the valence band, the doped holes are found to occupy mainly the ligand $p$ orbitals. Moreover, high hole doping leads to a significant reconstruction of the single-particle spectrum accompanied by a filling of the correlation gap.

Figure 1

(Color online) Theoretical $\mathrm{Ni}d$ (solid line) and $\mathrm{O}p$ (shaded) resolved spectral densities compared to photoemission and inverse-photoemission data obtained at 120 and $66\mathrm{eV}$ photon frequencies after Ref. 21. Gaussian broadening of $0.6\mathrm{eV}$ full width at half maximum corresponding to the experimental resolution was applied to the theoretical curves. The circle marks position of the $d^{10}\underset{̱}{L}$ excitation.

Figure 2

(Color online) Orbitally resolved $\mathrm{O}2p$ and $\mathrm{Ni}3d$ spectral densities (offset for better resolution). Substantial spectral weight transfer relative to the LDA results (see inset) is observed.

Figure 3

(Color online) $\mathrm{Ni}d$ and $\mathrm{O}p$ resolved spectral densities for a hole concentration $n_h=0.6$ (offset for better resolution). The inset shows a comparison of $e_g$ spectral densities for hole concentrations $n_h=0.6$ and 1.2.

Figure 4

(Color online) Theoretical $\mathrm{Ni}d$ spectral densities for electron addition and electron removal obtained for $n_h=0.6$ hole-doped NiO compared to the photoemission and inverse-photoemission spectra (Ref. 30) of ${\mathrm{Li}}_{0.4}{\mathrm{Ni}}_{0.6}\mathrm{O}$ (the experimental base line is offset for better readability).