NiO: Correlated Band Structure of a Charge-Transfer Insulator

The band structure of the prototypical charge-transfer insulator NiO is computed by using a combination of an ab initio band structure method and the dynamical mean-field theory with a quantum Monte-Carlo impurity solver. Employing a Hamiltonian which includes both Ni $d$ and O $p$ orbitals we find excellent agreement with the energy bands determined from angle-resolved photoemission spectroscopy. This brings an important progress in a long-standing problem of solid-state theory. Most notably we obtain the low-energy Zhang-Rice bands with strongly $\mathbf{k}$-dependent orbital character discussed previously in the context of low-energy model theories.

Figure 1

The $\mathbf{k}$-resolved total spectral function $A(\mathbf{k},\omega )$ along the $\Gamma \mathrm{\text{−}}X$ (upper panel) and $\Gamma \mathrm{\text{−}}K$ (lower panel) lines in the Brillouin zone depicted as a contour plot. The symbols represent the experimental bands of Shen et al. [4]. The theoretical gap edge was aligned with the experimental one.

Figure 2

The orbitally decomposed spectral function $A_{\nu \nu }(\mathbf{k},\omega )$ along the $\Gamma \mathrm{\text{−}}X$ (left column) and $\Gamma \mathrm{\text{−}}K$ (right column) lines in the Brillouin zone plotted as $\frac{A_{\nu \nu }(\mathbf{k},\omega )}{C+A_{\nu \nu }(\mathbf{k},\omega )}$. The panels from top to bottom show the O-$p$, Ni-$d-e_g$, and Ni-$d-t_{2g}$ contributions. Here $C=1.5$, 2 for the $p$ and $d$ projections, respectively. Detail of the uppermost valence band marked by the dotted lines is shown in Fig. 3.

Figure 3

Detail of the uppermost valence band along the $\Gamma \mathrm{\text{−}}K$ (right) and $\Gamma \mathrm{\text{−}}X$ (left) lines. The top panels show the O-$p$ contribution $A_{pp}(\mathbf{k},\omega )$, while Ni-$d$ contribution $A_{dd}(\mathbf{k},\omega )$ $A_{dd}(\mathbf{k},\omega )$ of the $e_g$ symmetry is shown in the bottom panels.