dorsal/arxiv
View SchemaFrom perovskite to infinite-layer nickelates: hole concentration from x-ray absorption
| Authors | R. Pons, M. Flavenot, K. Fürsich, E. Schierle, E. Weschke, M. R. Cantarino, E. Goering, P. Nagel, S. Schuppler, G. Kim, G. Logvenov, B. Keimer, R. J. Green, D. Preziosi, E. Benckiser |
|---|---|
| Categories | |
| ArXiv ID | 2601.07710vv1 |
| URL | https://arxiv.org/abs/2601.07710 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
The difficulty of determining cation concentrations and oxygen stoichiometry in infinite-layer nickelate thin films has so far prevented clear experimental identification of the nickel electron configuration in the superconducting phase. We used soft x-ray absorption spectroscopy to study the successive changes in PrNiO$_x$ thin films at various intermediate stages of topotactic reduction with $x=2-3$. By comparing the Ni-$L$ edge spectra to single and double cluster ligand-field calculations, we find that none of our samples exhibit a pure $d^9$ configuration. Our quantitative analysis using the charge sum rule shows that even when films are maximally reduced, the averaged number of nickel $3d$ holes is 1.35. Superconducting samples have even higher values, calling into question the previously assumed limit of hole doping. Concomitant changes in the oxygen $K$-edge absorption spectra upon reduction indicate the presence of oxygen $2p$ holes, even in the most reduced films. Overall, our results suggest a complex interplay of hole doping mechanisms resulting from self-doping effects and oxygen non-stoichiometry.
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"date_modified": "2026-02-17T05:53:12.529000Z",
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"abstract": "The difficulty of determining cation concentrations and oxygen stoichiometry in infinite-layer nickelate thin films has so far prevented clear experimental identification of the nickel electron configuration in the superconducting phase. We used soft x-ray absorption spectroscopy to study the successive changes in PrNiO$_x$ thin films at various intermediate stages of topotactic reduction with $x=2-3$. By comparing the Ni-$L$ edge spectra to single and double cluster ligand-field calculations, we find that none of our samples exhibit a pure $d^9$ configuration. Our quantitative analysis using the charge sum rule shows that even when films are maximally reduced, the averaged number of nickel $3d$ holes is 1.35. Superconducting samples have even higher values, calling into question the previously assumed limit of hole doping. Concomitant changes in the oxygen $K$-edge absorption spectra upon reduction indicate the presence of oxygen $2p$ holes, even in the most reduced films. Overall, our results suggest a complex interplay of hole doping mechanisms resulting from self-doping effects and oxygen non-stoichiometry.",
"arxiv_id": "2601.07710",
"authors": [
"R. Pons",
"M. Flavenot",
"K. F\u00fcrsich",
"E. Schierle",
"E. Weschke",
"M. R. Cantarino",
"E. Goering",
"P. Nagel",
"S. Schuppler",
"G. Kim",
"G. Logvenov",
"B. Keimer",
"R. J. Green",
"D. Preziosi",
"E. Benckiser"
],
"categories": [
"cond-mat.supr-con",
"cond-mat.mtrl-sci",
"cond-mat.str-el"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "From perovskite to infinite-layer nickelates: hole concentration from x-ray absorption",
"url": "https://arxiv.org/abs/2601.07710",
"version": "v1"
},
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"variant": "snapshot-2026-01-17",
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