Hubbard-U-corrected electron-phonon interactions in strongly correlated materials via the finite-displacement method

摘要

该论文将密度泛函理论加哈伯德U修正（DFT+U）与有限位移法相结合，实现了对强关联材料中声子谱和电子-声子矩阵的全哈伯德修正计算。作者将该方法应用于两种典型体系：无限层镍酸盐LaNiO₂和二氧化钌RuO₂。结果表明：在20%空穴掺杂的LaNiO₂中，哈伯德U修正微弱增强其电子-声子相互作用，但总耦合强度仍很小，不足以解释实验中约10-30 K的超导转变温度；这与近期GW修正预言的结果相反，差异源于DFT+U与GW方法所得费米面拓扑不同。在RuO₂中，哈伯德U修正消除了TiO₂衬底应变下的虚声子模，并大幅降低了电子-声子耦合，缓解了理论上过大的电子-声子耦合与实验观测到低超导转变温度之间的矛盾。该工作提供了完整纳入哈伯德U修正的电子-声子性质计算方案，并凸显了费米面形状及关联效应对声子谱和电子-声子矩阵的关键影响。

材料

• LaNiO₂
• RuO₂

方法

• DFT+U
• finite-displacement method
• electron-phonon coupling calculations

关键词

• electron phonon coupling
• hubbard u correction
• phonon hardening
• fermi surface topology

亮点

• Implements a fully self-consistent Hubbard-U correction to electron-phonon calculations using the finite-displacement method.
• Shows that partially corrected approaches (corrections only to electronic structure) can be qualitatively incorrect.
• Highlights the importance of Fermi surface shape and correlation effects on phonon spectra and electron-phonon matrices.

结论

• For 20% hole-doped LaNiO₂, Hubbard U corrections weakly increase electron-phonon coupling, but the total coupling remains too small to explain the observed T_c of 10-30 K.
• The discrepancy between DFT+U and GW methods is attributed to differences in Fermi surface topology.
• For TiO₂-strained RuO₂, Hubbard U corrections eliminate imaginary phonon modes and substantially reduce electron-phonon coupling, alleviating the discrepancy between theory and experiment.
• Correlation effects modify electron-phonon coupling through both electronic (Fermi surface) and phonon (hardening) channels.

主要论断

• Hubbard U corrections weakly increase electron-phonon coupling in LaNiO₂ but remain insufficient to explain observed T_c
  • 证据: From abstract: 'the Hubbard U corrections weakly increase the electron-phonon interaction of 20% hole-doped LaNiO₂, its total electron-phonon coupling remains small and is insufficient to account for the observed superconducting transition temperature of about 10-30 K'
• In RuO₂, Hubbard U corrections eliminate imaginary phonon modes and substantially reduce electron-phonon coupling, resolving discrepancy with experimental T_c
  • 证据: From abstract: 'The inclusion of Hubbard U corrections eliminates the imaginary phonon modes of RuO₂ under strain on the TiO₂ substrate and substantially reduces the electron-phonon coupling. Our results alleviate the discrepancy between the reported large theoretical electron-phonon coupling and the low superconducting transition temperature observed experimentally'

研究流程

• algorithm_implementation — Full Hubbard-U corrections implemented in electron-phonon calculations
  • 材料: DFT+U framework; finite-displacement method
  • 方法: integration of DFT+U with finite-displacement for phonons and e-ph matrices
  • 观察: phonon spectra; electron-phonon coupling
• application_to_LaNiO2 — Hubbard corrections weakly increase e-ph coupling but remain insufficient for observed T_c
  • 材料: 20% hole-doped LaNiO₂
  • 方法: DFT+U with finite-displacement
  • 观察: band structure; Fermi surface; electron-phonon coupling
• application_to_RuO2 — Hubbard corrections eliminate imaginary phonon modes and reduce e-ph coupling
  • 材料: TiO₂-strained RuO₂
  • 方法: DFT+U with finite-displacement
  • 观察: phonon stability; electron-phonon coupling