Cooperation between Electron-Phonon Coupling and Electronic Interaction in Bilayer Nickelates La₃Ni₂O₇

摘要

The recent observation of high-𝑇𝑐 superconductivity in the bilayer nickelate La₃⁢Ni₂⁢O₇ under pressure has garnered significant interest. While researches have predominantly focused on the role of electron-electron interactions in the superconducting mechanism, the impact of electron-phonon coupling (EPC) has remained elusive and unexplored. In this Letter, we perform first-principles calculations to study the phonon spectrum and electron-phonon coupling within La₃⁢Ni₂⁢O₇ under pressure and explore the interplay between EPC and electronic interactions on the superconductivity by employing functional renormalization group (FRG) approach. Our calculations reveal that EPC alone is insufficient to trigger superconductivity in La₃⁢Ni₂⁢O₇ under pressure. We identify unique out-of-plane and in-plane breathing phonon modes which selectively couple with the Ni 𝑑𝑧2 and 𝑑𝑥2−𝑦2 orbitals, showcasing an orbital-selective EPC. Within the bilayer two-orbital model, it is revealed that solely electronic interactions foster 𝑠±-wave pairing characterized by notable frustration in the band space, leading to a relatively low transition temperature. Remarkably, we find that the out-of-plane EPC can act in concert with electronic interactions to promote the interlayer pairing in the 𝑑𝑧2 orbital, partially releasing the pairing frustration and thus elevating 𝑇𝑐. In contrast, the inclusion of in-plane EPC only marginally affects the superconductivity, distinct from the cuprates. Potential experimental implications in La₃⁢Ni₂⁢O₇ are also discussed.

材料

• La₃Ni₂O₇

方法

• first-principles calculations
• functional renormalization group (FRG) approach

关键词

• electron phonon coupling (epc)
• orbital selective epc
• s± wave pairing
• pairing frustration
• interlayer pairing

亮点

• Cooperation between electron-phonon coupling and electronic interaction in bilayer nickelates.
• Potential experimental implications discussed.

结论

• EPC alone is insufficient to trigger superconductivity in La₃Ni₂O₇ under pressure.
• Unique out-of-plane and in-plane breathing phonon modes selectively couple with Ni dz2 and dx2-y2 orbitals, showcasing orbital-selective EPC.
• Within the bilayer two-orbital model, solely electronic interactions foster s±-wave pairing with notable frustration, leading to a relatively low transition temperature.
• Out-of-plane EPC can act in concert with electronic interactions to promote interlayer pairing in the dz2 orbital, partially releasing pairing frustration and elevating T_c.
• Inclusion of in-plane EPC only marginally affects superconductivity, distinct from cuprates.

主要论断

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研究流程

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