Stabilization of singlet hole-doped state in infinite-layer nickelate superconductors
Bibliographic record
Abstract
Motivated by the recent x-ray absorption spectroscopy 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, $\mathrm{Pr}){\mathrm{NiO}}_{2}$ by including the crystal field splitting, the $\mathrm{Ni}\text{\ensuremath{-}}3d$ multiplet structure, and the hybridization between $\mathrm{Ni}\text{\ensuremath{-}}3d, \mathrm{O}\text{\ensuremath{-}}2p$, and $\mathrm{Nd}\text{\ensuremath{-}}5d$ 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 band strongly hybridizing with the $\mathrm{Ni}\text{\ensuremath{-}}3{d}_{{z}^{2}}^{9}$ state. This hybridization pushes the main part of the $3{d}_{{z}^{2}}^{9}$ 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 $\mathrm{Ni}\text{\ensuremath{-}}3{d}_{{z}^{2}}^{9}$ 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 $\mathrm{Ni}\text{\ensuremath{-}}3{d}_{{z}^{2}}^{9}$ hole state, although the shape of the $\mathrm{Ni}\text{\ensuremath{-}}3{d}_{{z}^{2}}^{9}$ 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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".