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Bulk superconductivity near 40 K in hole-doped SmNiO2 at ambient pressure

Nature volume 642, pages 58–63 (2025)Cite this article

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Abstract

The discovery of superconductivity in the Ba-La-Cu-O system (the cuprate) in the 30 K range marked a significant breakthrough, which inspired extensive exploration of oxide-based, layered superconductors to identify electron pairing with higher critical temperatures (Tc)1. Despite recent observations of superconductivity in nickel oxide-based compounds (the nickelates), evidence of Cooper pairing above 30 K in a system that is isostructural to the cuprates, but without copper, at ambient pressure and without lattice compression has remained elusive2,3,4,5. Here we report superconductivity with a Tc approaching 40 K under ambient pressure in d9−x hole-doped, late rare earth, infinite-layer nickel oxide (Sm-Eu-Ca-Sr)NiO2 thin films with negligible lattice compression, supported by observations of a zero-resistance state at 31 K and the Meissner effect. The material can be synthesized with essentially no Ruddlesden–Popper-type structural defects, exhibiting ultralow resistivity of approximately 0.01 mΩ cm, and with a residual resistivity ratio of up to 10. Our findings demonstrate the potential for achieving high-temperature superconductivity using strongly correlated d-electron metal oxides beyond copper as the building blocks for superconductivity, and offering a promising platform for further exploration and understanding of high-temperature Cooper pairing.

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Fig. 1: Structural information on the superconducting SECS nickel oxide thin films.
Fig. 2: Transport characteristics of the superconducting SECS nickel oxide thin films.
Fig. 3: Zero resistance and diamagnetic state in the SECS nickel oxide thin film.
Fig. 4: Meissner state in the SECS nickel oxide thin films.
Fig. 5: Discoveries of superconducting d9−x nickel oxides.

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Data availability

The data that support the findings of this study are provided in the manuscript and Supplementary Information. All other relevant data are available from the corresponding authors.

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Acknowledgements

We specially thank S.W. Zeng who developed the infinite-layer nickelate thin-film fabrication process at the National University of Singapore. The Ca/Sr-doped (La/Sm/Eu/Gd)NiO2 superconducting nickelate projects were originally initiated by S.W. Zeng and A. Ariando in 2020. We also thank Q. He who has supported the electron microscopy training for Z.Y. Luo. We acknowledge technical support from S.W. Zeng, Z.T. Zhang, P. Nandi, S.S. Kunniniyil, S. Prakash, Y. Ping, N. Fitriyah, X. Gao, J.B. Luo, K.Y. Yip, N.H. Teo, Z.S. Lim, G.J. Omar, X.M. Du, and D.D. Guo. We acknowledge useful discussions with E.E.M. Chia, K. Heldt, H.J.W.M. Hilgenkamp, H. Jani, K. Kuroki, F. Lechermann, K. Lee, D. Li, G. Sawatzky, D.F. Segedin, B.Y. Wang, X.R. Wang, W. Wei, Y.-F. Yang, and Y. Yu. This research is supported by the Ministry of Education (MOE), Singapore, under its Tier-2 Academic Research Fund (AcRF), grant no. MOE-T2EP50121-0018 and MOE-T2EP50123-0013, by the MOE Tier-3 Grant (MOE-MOET32023-0003) ‘Quantum Geometric Advantage’ and by the SUSTech-NUS Joint Research Program. S.L.E.C. acknowledges support from the President’s Graduate Fellowship provided by the National University of Singapore. The authors acknowledge the Singapore Synchrotron Light Source (SSLS) for providing the facility necessary for conducting the research. The laboratory is a National Research Infrastructure under the National Research Foundation (NRF) Singapore.

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Authors and Affiliations

  1. Department of Physics, Faculty of Science, National University of Singapore, Singapore, Singapore

    S. Lin Er Chow, Zhaoyang Luo & A. Ariando

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  1. S. Lin Er Chow
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  2. Zhaoyang Luo
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Contributions

S.L.E.C. and A.A. conceived the project and designed the experiments. S.L.E.C. synthesized the nickelate films conducted the transport characterization and performed the susceptibility measurements. Z.L. conducted the structural analysis of the films, performed X-ray diffraction experiments, prepared the focused-ion beam specimen, and performed electron microscopy characterization. All authors analysed and discussed the data and wrote the manuscript. A.A. secured the grants and supervised the entire project.

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Correspondence to S. Lin Er Chow or A. Ariando.

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Extended data figures and tables

Extended Data Fig. 1 Structural analysis data.

Low-magnification STEM-HAADF and Fast-Fourier-Transform (FFT) images of the representative superconducting Sm0.79Eu0.12Ca0.04Sr0.05NiO2 thin film.

Extended Data Fig. 2 Additional structural analysis data.

STEM-HAADF images show several areas of the representative Sm0.79Eu0.12Ca0.04Sr0.05NiO2 thin film. The infinite-layer film is virtually free of RP-type structural defects.

Extended Data Fig. 3 Curvature of the resistivity \({\boldsymbol{\rho }}({\boldsymbol{T}}\,)\) curve \(\frac{{{\boldsymbol{\partial }}}^{{\bf{2}}}{\boldsymbol{\rho }}}{{\boldsymbol{\partial }}{{\boldsymbol{T}}}^{{\bf{2}}}}\) in Fig. 2b.

The superconducting transition ends with zero resistance state at 31 K. Inset shows the magnification of the \(\frac{{\partial }^{2}\rho }{\partial {T}^{2}}\) near the onset.

Extended Data Fig. 4 Comparison of the resistivity \({\boldsymbol{\rho }}({\boldsymbol{T}})\) curves between different dopant concentrations.

a, Sm0.73Eu0.2Ca0.07NiO2 (h = 0.19) with Tc,0 = 26.5 K. b, Sm0.53Eu0.4Ca0.07NiO2 (h = 0.31) which is outside of superconducting phase. The overdoped Sm0.53Eu0.4Ca0.07NiO2 is completely metallic at all temperatures, with a low residual resistivity \({\rho }_{0}=0.0108\,{\rm{m}}\Omega \,\bullet \,{\rm{cm}}\) and a residual-resistivity-ratio RRR ~10.

Extended Data Fig. 5 Raw magnetization data.

The M-T data measured at applied field \({\boldsymbol{H}}\parallel {\boldsymbol{c}}={\bf{2.9}},{\bf{3.6}},{\bf{9.7}}\) Oe of a representative Sm0.75Eu0.2Ca0.05NiO2 thin film.

Extended Data Fig. 6 Magnetic hysteresis loop.

Small superconducting M-H loops of the representative Sm0.75Eu0.2Ca0.05NiO2 thin film shown in Fig. 3 with diamagnetism observed below 27 K.

Extended Data Fig. 7 Normal state Hall coefficients of SECS thin films.

a, Hall coefficients versus temperature \({R}_{H}(T\,)\) plot. b, Majority holes versus electrons phase diagram of various infinite-layer nickelates \(({\rm{R}},{\rm{A}}){\rm{Ni}}{{\rm{O}}}_{2}\) showing RH sign crossover temperature Th as a function of hole doping, adapted from refs. 16,17,18,59. For Sm1-x-y-zEuxCaySrzNiO2, hole doping is estimated as \(h=0.6x+y+z\) (ref. 19). c, Maximum Th as a function of rare earth ions (R) from La – Sm.

Supplementary information

Supplementary Information

Supplementary discussion, Tables 1 and 2, Figs. 1–7 and references.

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Chow, S.L.E., Luo, Z. & Ariando, A. Bulk superconductivity near 40 K in hole-doped SmNiO2 at ambient pressure. Nature 642, 58–63 (2025). https://doi.org/10.1038/s41586-025-08893-4

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