Late transition metal oxides with infinite-layer structure: Nickelates versus cuprates

The correlated electronic structure of the infinite-layer compounds NdNiO₂ and SrCuO₂ at stoichiometry and with finite hole doping is compared. Key differences are elucidated from an advanced first-principles many-body perspective. Contrary to the charge-transfer insulating cuprate, the self-doped nickelate remains noninsulating even for large interaction strength, though the Ni-d_x²-y² spectral weight is also gapped in that limit. Hybridization between Ni(3d) and Nd(5d) is crucial for the appearance of the self-doping band. Upon realistic hole doping, Sr_1-yCuO₂ shows the expected mixed oxygen-Cu-d_x²-y² (Zhang-Rice) states at low energy. In the case of Nd_1-xSrₓNiO₂, the self-doping band is shifted to higher energies and a doping-dependent d_z²-versus-d_x²-y² competition on Ni is revealed. The absence of prominent Zhang-Rice physics in infinite-layer nickelates might be relevant to understand the notable difference in the superconducting Tc's.