Bulk superconductivity near 40 K in hole-doped SmNiO<sub>2</sub> at ambient pressure.

Chow, S Lin Er; Luo, Zhaoyang; Ariando, A · Nature · 2025

basic_science · Level V

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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 (T<sub>c</sub>)<sup>1</sup>. 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 elusive<sup>2-5</sup>. Here we report superconductivity with a T<sub>c</sub> approaching 40 K under ambient pressure in d<sup>9-x</sup> hole-doped, late rare earth, infinite-layer nickel oxide (Sm-Eu-Ca-Sr)NiO<sub>2</sub> 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.