Daily Overview: Today’s highlight work focuses on the s+id mixed superconducting state induced by the synergistic effect of electronic correlations and electron-phonon coupling in infinite-layer nickelate superconductors. Investigations based on a combination of first-principles calculations and the fluctuation-exchange Migdal-Eliashberg theory reveal that spin fluctuations drive robust d-wave pairing in the Ni d_{x^2-y^2} orbital, while electron-phonon coupling induces an s-wave component in the interstitial orbitals. These two mechanisms synergistically form an s+id mixed superconducting state at a specific carrier density (e.g., n=0.9). The stability of this mixed state is highly sensitive to the local electron density. Local oxygen defects, by modulating the electron density, can create finite-sized domains with different pairing symmetries, thereby providing a microscopic explanation for the spatially inhomogeneous superconducting gap observed experimentally. These results profoundly underscore the crucial role of the synergy between correlation effects and electron-phonon coupling in determining the pairing symmetry of nickelate superconductors. arXiv submission processing window: 2026-07-15 00:00 to 2026-07-15 00:00 UTC.
1. Emergent $s+id$ Superconductivity from the Interplay between Electronic Correlations and Electron-Phonon Coupling in $\mathrm{R}_{1-x}\mathrm{Sr}_x\mathrm{NiO}_2$
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5.2003 - Authors: Zi Yuan, Jun Zhan, Xianxin Wu, Shaozhi Li
- Link: https://arxiv.org/abs/2607.12773
- Paper page: Emergent s+id Superconductivity from the Interplay between Electronic Correlations and Electron-Phonon Coupling in R₁₋ₓSrₓNiO₂
Summary: Combining first-principles calculations with fluctuation exchange-Migdal-Eliashberg theory, this study investigates the interplay between electron correlations and electron-phonon coupling in infinite-layer nickelate superconductors. The results show that spin fluctuations drive robust d-wave superconductivity in the Ni d_{x^2-y^2} orbital, while electron-phonon coupling induces s-wave pairing in interstitial orbitals, and their synergy gives rise to a mixed s+id superconducting state. The emergence of the s-wave component strongly depends on carrier density: a moderate electron-phonon coupling strength (λ=0.4) stabilizes the mixed state only at an electron density n=0.9, but not at n=0.8. In the thermodynamic limit, the critical coupling required to stabilize the s-wave component is about 0.6, but it can be reduced to 0.4 in finite-size systems. These results reveal that local oxygen defects, by modulating the local electron density, can form finite-size domains with distinct pairing symmetries, thereby providing a microscopic explanation for the spatially inhomogeneous superconducting gaps observed experimentally, and highlight the crucial influence of the cooperative effect of electron correlations and electron-phonon coupling on the pairing symmetry in nickelate superconductors.