The low-energy properties of transition metal oxides (TMOs) are governed by the electrons occupying strongly correlated $d$-orbitals that are hybridized with surrounding ligand oxygen $p$ orbitals to varying degrees. Their physics is thus established by a complex interplay between the transition-metal (TM)-ligand hopping $t$, charge transfer energy ${\mathrm{\Delta }}_{\mathrm{CT}}$, and on-site TM Hubbard repulsion $U$. Here, we study the spectral properties of a one-dimensional analog of such a $pd$ system, with alternating TM $d$ and ligand anion $p$ orbitals situated along a chain. Using the density matrix renormalization group method, we study the model's single-particle spectral function, x-ray absorption spectrum, and dynamical spin structure factor as a function of ${\mathrm{\Delta }}_{\mathrm{CT}}$ and $U$. In particular, we present results spanning from the Mott insulating (${\mathrm{\Delta }}_{\mathrm{CT}}>U$) to negative charge transfer regime ${\mathrm{\Delta }}_{\mathrm{CT}}<0$ to better understand the ground-state and momentum-resolved excited-state properties of these different regimes. Our results can guide new studies on TMOs that seek to situate them within the Mott-Hubbard/charge transfer insulator classification scheme.

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• Density matrix renormalization group
• Metal-insulator transition
• 1-dimensional systems
• Charge-transfer insulators