Sun, H. et al. Signatures of superconductivity near 80 K in a nickelate under high pressure. Nature 621, 493–498 (2023).
Hou, J. et al. Emergence of high-temperature superconducting phase in pressurized La3Ni2O7 crystals. Chin. Phys. Lett. 40, 117302 (2023).
Zhang, Y. et al. High-temperature superconductivity with zero-resistance and strange metal behavior in La3Ni2O7. Preprint at https://doi.org/10.48550/arXiv.2307.14819 (2023).
Liu, Z. et al. Electronic correlations and energy gap in the bilayer nickelate La3Ni2O7. Preprint at https://doi.org/10.48550/arXiv.2307.02950 (2023).
Yang, J. et al. Orbital-dependent electron correlation in double-layer nickelate La3Ni2O7. Preprint at https://doi.org/10.48550/arXiv.2309.01148 (2023).
Zhou, Y. et al. Evidence of filamentary superconductivity in pressurized La3Ni2O7 single crystals. Preprint at https://doi.org/10.48550/arXiv.2311.12361 (2023).
Yang, Y., Zhang, G.-M. & Zhang, F.-C. Interlayer valence bonds and two-component theory for high-Tc superconductivity of La3Ni2O7 under pressure. Phys. Rev. B 108, L201108 (2023).
Qin, Q. & Yang, Y. High-Tc superconductivity by mobilizing local spin singlets and possible route to higher Tc in pressurized La3Ni2O7. Phys. Rev. B 108, L140504 (2023).
Shen, Y., Qin, M. & Zhang, G.-M. Effective bi-layer model Hamiltonian and density-matrix renormalization group study for the high-Tc superconductivity in La3Ni2O7 under high pressure. Chin. Phys. Lett. 40, 127401 (2023).
Gu, Y., Le, C., Yang, Z., Wu, X. & Hu, J. Effective model and pairing tendency in bilayer Ni-based superconductor La3Ni2O7. Preprint at https://doi.org/10.48550/arXiv.2306.07275 (2023).
Yang, Q.-G., Wang, D. & Wang, Q.-H. Possible s±-wave superconductivity in La3Ni2O7. Phys. Rev. B 108, L140505 (2023).
Qu, X.-Z. et al. Bilayer t–J–J⟂ model and magnetically mediated pairing in the pressurized nickelate La3Ni2O7. Phys. Rev. Lett. 132, 036502 (2024).
Liu, Y.-B., Mei, J.-W., Ye, F., Chen, W.-Q. & Yang, F. s±-wave pairing and the destructive role of apical-oxygen deficiencies in La3Ni2O7 under pressure. Phys. Rev. Lett. 131, 236002 (2023).
Zhang, Y., Lin, L.-F., Moreo, A., Maier, T. A. & Dagotto, E. Electronic structure, magnetic correlations, and superconducting pairing in the reduced Ruddlesden–Popper bilayer La3Ni2O6 under pressure: different role of d3z2−r2 orbital compared with La3Ni2O7. Phys. Rev. B 109, 045151 (2024).
Anisimov, V. I., Bukhvalov, D. & Rice, T. M. Electronic structure of possible nickelate analogs to the cuprates. Phys. Rev. B 59, 7901–7906 (1999).
Lee, K.-W. & Pickett, W. E. Infinite-layer LaNiO2: Ni1+ is not Cu2+. Phys. Rev. B 70, 165109 (2004).
Li, D. et al. Superconductivity in an infinite-layer nickelate. Nature 572, 624–627 (2019).
Wang, N. N. et al. Pressure-induced monotonic enhancement of Tc to over 30 K in superconducting Pr0.82Sr0.18NiO2 thin films. Nat. Commun. 13, 4367 (2022).
Lee, K. et al. Linear-in-temperature resistivity for optimally superconducting (Nd,Sr)NiO2. Nature 619, 288–292 (2023).
Song, D. et al. Visualization of dopant oxygen atoms in a Bi2Sr2CaCu2O8+δ superconductor. Adv. Funct. Mater. 29, 1903843 (2019).
Close, R., Chen, Z., Shibata, N. & Findlay, S. D. Towards quantitative, atomic-resolution reconstruction of the electrostatic potential via differential phase contrast using electrons. Ultramicroscopy 159, 124–137 (2015).
Findlay, S. D. et al. Dynamics of annular bright field imaging in scanning transmission electron microscopy. Ultramicroscopy 110, 903–923 (2010).
Chen, Z. et al. Electron ptychography achieves atomic-resolution limits set by lattice vibrations. Science 372, 826–831 (2021).
Hüe, F., Rodenburg, J. M., Maiden, A. M., Sweeney, F. & Midgley, P. A. Wave-front phase retrieval in transmission electron microscopy via ptychography. Phys. Rev. B 82, 121415 (2010).
Zaanen, J., Sawatzky, G. A. & Allen, J. W. Band gaps and electronic structure of transition-metal compounds. Phys. Rev. Lett. 55, 418–421 (1985).
Hepting, M. et al. Electronic structure of the parent compound of superconducting infinite-layer nickelates. Nat. Mater. 19, 381–385 (2020).
Goodge, B. H. et al. Doping evolution of the Mott–Hubbard landscape in infinite-layer nickelates. Proc. Natl Acad. Sci. USA 118, e2007683118 (2021).
Jiang, Y. et al. Electron ptychography of 2D materials to deep sub-ångström resolution. Nature 559, 343–349 (2018).
Voronin, V. I. et al. Neutron diffraction, synchrotron radiation and EXAFS spectroscopy study of crystal structure. Nuclear 470, 202–209 (2001).
Sui, X. et al. Electronic properties of nickelate superconductor R3Ni2O7 with oxygen vacancies. Preprint at https://doi.org/10.48550/arXiv.2312.01271 (2023).
Geisler, B. et al. Optical properties and electronic correlations in La3Ni2O7-δ bilayer nickelates under high pressure. Preprint at https://doi.org/10.48550/arXiv.2401.04258 (2024).
Liu, Z. et al. Evidence for charge and spin density waves in single crystals of La3Ni2O7 and La3Ni2O6. Sci. China Phys. Mech. Astron. 66, 217411 (2023).
Pellegrin, E. et al. O 1s near-edge X-ray absorption of La2−xSrxNiO4+δ: holes, polarons, and excitons. Phys. Rev. B 53, 10667–10679 (1996).
Abbate, M. et al. Electronic structure and metal–insulator transition in LaNiO3−δ. Phys. Rev. B 65, 155101 (2002).
Bisogni, V. et al. Ground-state oxygen holes and the metal–insulator transition in the negative charge-transfer rare-earth nickelates. Nat. Commun. 7, 13017 (2016).
Lu, Y. et al. Site-selective probe of magnetic excitations in rare-earth nickelates using resonant inelastic X-ray scattering. Phys. Rev. X 8, 031014 (2018).
Lechermann, F., Gondolf, J., Bötzel, S. & Eremin, I. M. Electronic correlations and superconducting instability in La3Ni2O7 under high pressure. Phys. Rev. B 108, L201121 (2023).
Chen, X., Jiang, P., Li, J., Zhong, Z. & Lu, Y. Critical charge and spin instabilities in superconducting La3Ni2O7. Preprint at https://doi.org/10.48550/arXiv.2307.07154 (2023).
Shilenko, D. A. & Leonov, I. V. Correlated electronic structure, orbital-selective behavior, and magnetic correlations in double-layer La3Ni2O7 under pressure. Phys. Rev. B 108, 125105 (2023).
Zhang, F. C. & Rice, T. M. Effective Hamiltonian for the superconducting Cu oxides. Phys. Rev. B 37, 3759–3761 (1988).
Wú, W., Luo, Z., Yao, D.-X. & Wang, M. Superexchange and charge transfer in the nickelate superconductor La3Ni2O7 under pressure. Sci. China Phys. Mech. Astron. 67, 117402 (2024).
Ruan, W. et al. Relationship between the parent charge transfer gap and maximum transition temperature in cuprates. Sci. Bull. 61, 1826–1832 (2016).
O’Mahony, S. M. et al. On the electron pairing mechanism of copper-oxide high temperature superconductivity. Proc. Natl Acad. Sci. USA 119, e2207449119 (2022).
Pan, G. A. et al. Synthesis and electronic properties of Ndn+1NinO3n+1 Ruddlesden–Popper nickelate thin films. Phys. Rev. Mater. 6, 055003 (2022).
Bocquet, A. E., Mizokawa, T., Saitoh, T., Namatame, H. & Fujimori, A. Electronic structure of 3d-transition-metal compounds by analysis of the 2p core-level photoemission spectra. Phys. Rev. B 46, 3771–3784 (1992).
Pan, G. A. et al. Superconductivity in a quintuple-layer square-planar nickelate. Nat. Mater. 21, 160–164 (2022).
Chen, C. T. et al. Electronic states in La2−xSrxCuO4+δ probed by soft-X-ray absorption. Phys. Rev. Lett. 66, 104–107 (1991).
Zhang, Z., Greenblatt, M. & Goodenough, J. B. Synthesis, structure, and properties of the layered perovskite La3Ni2O7−δ. J. Solid State Chem. 108, 402–409 (1994).
Taniguchi, S. et al. Transport, magnetic and thermal properties of La3Ni2O7−δ. J. Phys. Soc. Jpn 64, 1644–1650 (1995).
Zhang, J. et al. High oxygen pressure floating zone growth and crystal structure of the metallic nickelates R4Ni3O10 (R = La,Pr). Phys. Rev. Mater. 4, 083402 (2020).
Wang, H., Chen, L., Rutherford, A., Zhou, H. & Xie, W. Long-range structural order in a hidden phase of Ruddlesden–Popper bilayer nickelate La3Ni2O7. Inorg. Chem. 63, 5020–5026 (2024).
Chen, X. et al. Polymorphism in the Ruddlesden–Popper nickelate La3Ni2O7: discovery of a hidden phase with distinctive layer stacking. J. Am. Chem. Soc. 146, 3640–3645 (2024).
Puphal, P. et al. Unconventional crystal structure of the high-pressure superconductor La3Ni2O7. Preprint at https://doi.org/10.48550/arxiv.2312.07341 (2023).
Robert, H. L., Diederichs, B. & Müller-Caspary, K. Contribution of multiple plasmon scattering in low-angle electron diffraction investigated by energy-filtered atomically resolved 4D-STEM. Appl. Phys. Lett. 121, 213502 (2022).
Allen, L. J., D’Alfonso, A. J. & Findlay, S. D. Modelling the inelastic scattering of fast electrons. Ultramicroscopy 151, 11–22 (2015).
Bürger, J., Riedl, T. & Lindner, J. K. N. Influence of lens aberrations, specimen thickness and tilt on differential phase contrast STEM images. Ultramicroscopy 219, 113118 (2020).
Malis, T., Cheng, S. C. & Egerton, R. F. EELS log-ratio technique for specimen-thickness measurement in the TEM. J. Electron Microsc. Tech. 8, 193–200 (1988).
Blaha, P. et al. WIEN2k: an APW+lo program for calculating the properties of solids. J. Chem. Phys. 152, 074101 (2020).
Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).
Dong, Z., Chen, Z. & Wang, Y. Dataset for: visualization of oxygen vacancies and self-doped ligand holes in La3Ni2O7−δ. Zenodo https://doi.org/10.5281/zenodo.10947322 (2024).
Chen, Z., Jiang, Y., Muller, D. A. & Odstrcil, M. PtychoShelves_EM, source code for multislice electron ptychography. Zenodo https://doi.org/10.5281/zenodo.4659690 (2021).
