Persistent paramagnons in high-temperature infinite-layer nickelate superconductors

Yujie Yan; Ying Chan; Xunyang Hong; S. Lin Er Chow; Zhaoyang Luo; Yuehong Li; Tianren Wang; Yuetong Wu; Izabela Biało; Nurul Fitriyah; Saurav Prakash; Xing Gao; King Yau Yip; Qiang Gao; Xiaolin Ren; Jaewon Choi; Ganesha Channagowdra; Jun Okamoto; Xingjiang Zhou; Zhihai Zhu; Liang Si; Mirian Garcia-Fernandez; Ke-Jin Zhou; Hsiao-Yu Huang; Di-Jing Huang; Johan Chang; A. Ariando; Qisi Wang

doi:10.1038/s41467-026-73083-3

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arXiv · 2507.18373

Persistent paramagnons in high-temperature infinite-layer nickelate superconductors

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Abstract

The recent discovery of high-temperature superconductivity in hole-doped SmNiO$_2$, exhibiting the record-high transition temperature $T_c$ among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity. Here, we report a Ni $L$-edge resonant inelastic x-ray scattering (RIXS) study of superconducting Sm-based IL nickelate thin films Sm$_{1-x-y-z}$Eu$_x$Ca$_y$Sr$_z$NiO$_2$ (SECS). Dispersive paramagnonic excitations are observed in both optimally and overdoped SECS samples, supporting a spin-fluctuation-mediated pairing scenario. However, despite the two-fold enhancement of $T_c$ in the Sm-based nickelates compared to their Pr-based counterparts, the effective exchange coupling strength is reduced by approximately $20\%$. This behavior contrasts with hole-doped cuprates, where magnetic interactions correlate positively with $T_c$, highlighting essential differences in their superconducting mechanisms.

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Yujie Yan, Ying Chan, Xunyang Hong, S. Lin Er Chow, Zhaoyang Luo, Yuehong Li, Tianren Wang, Yuetong Wu, Izabela Biało, Nurul Fitriyah, Saurav Prakash, Xing Gao, King Yau Yip, Qiang Gao, Xiaolin Ren, Jaewon Choi, Ganesha Channagowdra, Jun Okamoto, Xingjiang Zhou, Zhihai Zhu, Liang Si, Mirian Garcia-Fernandez, Ke-Jin Zhou, Hsiao-Yu Huang, Di-Jing Huang, Johan Chang, A. Ariando, Qisi Wang. 2025-07-24. Persistent paramagnons in high-temperature infinite-layer nickelate superconductors. https://doi.org/10.1038/s41467-026-73083-3

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