Prediction of several Co-based La₃Ni₂O₇-like superconducting materials

摘要

通过电子掺杂高压双层钴酸盐La₃Co₂O₇，预测了LaTh₂Co₂O₇、La₃Ni₂O₅Cl₂和La₃Ni₂O₅Br₂等钴基La₃Ni₂O₇类似物，这些材料具有相似的晶体结构和强关联电子态。基于密度泛函理论加动力学平均场理论（DFT+DMFT）和随机相位近似（RPA）的计算表明，钴的3d轨道呈现半满或接近半满的占据，与La₃Ni₂O₇中镍的轨道类似，并表现出强Hund耦合和质量增强。这些钴基化合物的局域磁矩（约0.64 μ_B）恰好落在镍酸盐超导的最佳窗口内（0.63–0.68 μ_B），强烈暗示其可能通过类似的自旋涨落机制实现高温超导。RPA计算进一步揭示，在电子掺杂的钴酸盐中，领先的配对对称性为s波，属于A₁ᵍ不可约表示。该工作为在钴基体系中实现高温超导电性提供了理论依据，并鼓励进一步的实验合成和表征。

材料

• LaTh₂Co₂O₇
• La₃Ni₂O₅Cl₂
• La₃Ni₂O₅Br₂

方法

• DFT+DMFT
• RPA
• tight-binding modeling

关键词

• cobaltate superconductors
• hund's coupling
• s wave pairing
• electron doping

亮点

• First prediction of La₃Ni₂O₇-like high-temperature superconductivity in cobalt-based materials.
• Shows that electron doping of La₃Co₂O₇ can achieve electronic structure similar to La₃Ni₂O₇.
• Provides theoretical basis for experimental synthesis of new cobaltate superconductors.

结论

• Electron-doped bilayer cobaltates (LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, La₃Ni₂O₅Br₂) are predicted to be strongly correlated analogs of La₃Ni₂O₇.
• Co 3d orbitals are half-filled or near-half-filled, exhibiting strong Hund coupling and mass enhancement.
• Local magnetic moments (0.64 μB) fall within the optimal window for nickelate superconductivity.
• RPA calculations reveal s-wave as the leading pairing symmetry (A₁g representation).

主要论断

• Co-based La₃Ni₂O₇ analogs (LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, La₃Ni₂O₅Br₂) exhibit similar crystal structures and strongly correlated electronic states
  • 证据: From abstract: 'Electron doping of the high-pressure bilayer cobaltate La₃Co₂O₇ yields LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, and La₃Ni₂O₅Br₂, which exhibit closely related crystal structures and strongly correlated electronic states'
• Random-phase-approximation calculations reveal s-wave as the leading pairing symmetry in these compounds
  • 证据: From abstract: 'Random-phase-approximation calculations reveal s-wave as the leading pairing symmetry in these compounds'
• Local magnetic moments (0.64 μ_B) fall within the optimal window for nickelate superconductivity (0.63-0.68 μ_B)
  • 证据: From text: 'local magnetic moments we calculate for these cobalt-based compounds—ranging from 0.637 to 0.647—fall precisely within the narrow window (0.63–0.68) recently identified as optimal for high-T_c superconductivity'

研究流程

• density_functional_theory_calculations — Co-based compounds isostructural to La₃Ni₂O₇
  • 材料: La₃Co₂O₇; LaTh₂Co₂O₇; La₃Ni₂O₅Cl₂; La₃Ni₂O₅Br₂
  • 方法: DFT with PBE functional; structural optimization
  • 观察: crystal structures; band structures
• dynamical_mean_field_theory_calculations — Co compounds exhibit strong correlations similar to La₃Ni₂O₇
  • 材料: Optimized structures
  • 方法: DFT+DMFT
  • 观察: spectral function; self-energy; local moments
• random_phase_approximation_analysis — s-wave is leading pairing symmetry in electron-doped cobaltates
  • 材料: Tight-binding models from DFT
  • 方法: RPA for pairing symmetry
  • 观察: leading pairing eigenvalues; gap symmetry