Stabilization of singlet hole-doped state in infinite-layer nickelate superconductors

Abstract

Motivated by the recent X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) experiments, we use a detailed impurity model to explore the nature of the parent compound and hole doped states of (La, Nd, Pr)NiO${}_2$ by including the crystal field splitting, the Ni-$3d$ multiplet structure, and the hybridization between Ni-$3d$, O-$2p$, and Nd-$5d$ orbitals. For simplicity and stimulated by the recent electronic structure calculations, the latter are formally replaced with symmetric orbitals centered at the missing O sites in the Nd layer, forming a two-dimensional (2D) band strongly hybridizing with the Ni-$3d_{z^2}^9$ state. This hybridization pushes the main part of the $3d_{z^2}^9$ spectral function up in energy by several eV and stabilizes the singlet with considerable $d_{z^2}^9$ and other configurational components. For the parent compound, we find that states of Ni-$3d_{z^2}^9$ character spread over a large energy range in the spectra, and cannot and should not be represented by a single orbital energy, as suggested in other approximations. This is qualitatively consistent with the RIXS measurements showing a broad distribution of the Ni-$3d_{z^2}^9$ hole state, although the shape of the Ni-$3d_{z^2}^9$ related structure is much more complicated requiring reinterpretations of the RIXS data. For the hole-doped systems, we show that adding these additional ingredients can still result in the lowest-energy hole doped state having a singlet character.

13 pages, 8 figures

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• Distinct electridelike nature of infinite-layer nickelates and the resulting theoretical challenges to calculate their electronic structure
• Intertwined charge and spin instability of La${}_3$Ni${}_2$O${}_7$
• Two Distinct Charge Orders in Infinite-layer PrNiO2+δ revealed by Resonant X-ray Diffraction
• Inversion symmetry breaking in bilayer multi-orbital Hubbard model with impurity approximation
• Quasiparticle approach to the transport in infinite-layer nickelates