Intriguing analogies between the nickelates and the cuprates provide a promising avenue for unraveling the microscopic mechanisms underlying high-$T_c$ superconductivity. While electron correlation effects in the nickelates have been extensively studied, the role of electron-phonon coupling (EPC) remains highly controversial. Here, by taking pristine ${\mathrm{LaNiO}}_2$ as an exemplar nickelate, we present an in-depth study of EPC for both the nonmagnetic (NM) and the $C$-type antiferromagnetic ($C$-AFM) phases using advanced density functional theory methods without invoking $U$ or other free parameters. The weak EPC strength $\lambda$ in the NM phase is found to be greatly enhanced ($\sim 4\times$) due to the presence of magnetism in the $C$-AFM phase. This enhancement arises from strong interactions between the flat $\mathrm{Ni}\text{−}3d{z}^2$ bands and the low-frequency phonon modes associated with Ni and La vibrations, rather than solely from the high-frequency oxygen breathing modes. The resulting phonon softening is shown to yield a distinctive kink in the electronic structure around 15 meV, which would provide an experimentally testable signature of our predictions. Our study highlights the critical role of local magnetic moments and EPC in the nickelate.

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• Electron-phonon coupling
• Electronic structure
• Flat bands
• Nickelates
• Density functional theory