Electronic structure and correlation of La₄Co₂NiO₈Cl₂: a theoretical proposal for a La₄Ni₃O₁₀-like high-temperature superconductor

摘要

基于对三层镍酸盐La₄Ni₃O₁₀高压超导的发现，该研究利用密度泛函理论结合动力学平均场理论（DFT+DMFT）设计并计算了钴基类似物La₄Co₂NiO₈Cl₂。通过将高压相La₄Co₃O₁₀内层Co替换为Ni并掺入Cl实现电子掺杂，该化合物获得了与超导La₄Ni₃O₁₀相似的晶体结构及强关联电子特征：外层Co轨道呈现强有效质量增强和非费米液体行为，内层Ni则表现为弱关联费米液体；在M点附近出现源于外层Co轨道且接近费米能级的平带；同时具有显著的轨道选择性以及高自旋与低自旋态混合的局域自旋涨落。这些特性与La₄Ni₃O₁₀的关键电子态高度吻合，表明La₄Co₂NiO₈Cl₂有望成为钴基层状化合物中实现高温超导电性的候选材料，为后续实验探索提供了理论依据。

材料

• La₄Co₂NiO₈Cl₂
• La₄Ni₃O₁₀

方法

• Density functional theory + dynamical mean-field theory (DFT+DMFT)

关键词

• orbital selectivity
• hund's metal
• flat bands
• non fermi liquid
• layer dependent correlation

亮点

• This work establishes La₄Co₂NiO₈Cl₂ as a promising candidate for hosting high-temperature superconductivity in cobalt-based layered compounds.
• Provides a theoretical basis for future experimental exploration of Co-based analogs.

结论

• La₄Co₂NiO₈Cl₂ exhibits electronic structure and correlation strength similar to those of superconducting La₄Ni₃O₁₀.
• The outer-layer Co orbitals exhibit strong effective mass enhancement and non-Fermi liquid behavior, while the inner-layer Ni behaves as a weakly correlated Fermi liquid.
• A flat band near the Fermi level originating from the outer-layer Co orbitals emerges around the M point.
• Pronounced orbital selectivity and local spin fluctuations mixing high-spin and low-spin states are present.

主要论断

• La₄Co₂NiO₈Cl₂ exhibits a crystal structure and strongly correlated electronic characteristics similar to those of superconducting La₄Ni₃O₁₀, including layer-dependent correlation and flat bands near the Fermi level.
  • 证据: Abstract: 'this compound acquires a crystal structure and strongly correlated electronic characteristics similar to those of superconducting La₄Ni₃O₁₀'
• The strong correlation character resides in the outer-layer Co sites, suggesting Co can play an active role in unconventional superconductivity.
  • 证据: Abstract: 'the outer-layer Co orbitals exhibit strong effective mass enhancement and non-Fermi liquid behavior' and Discussion: 'the outer-layer Co sites host the strong correlation essential for superconductivity'

研究流程

• Structural optimization
  • 材料: La₄Co₂NiO₈Cl₂ based on high-pressure La₄Ni₃O₁₀ structure
  • 方法: DFT (VASP) with GGA-PBE
  • 观察: Optimized lattice parameters: a=b=3.6116 Å, c=26.0039 Å
• Electronic structure calculation — La₄Co₂NiO₈Cl₂ exhibits electronic structure similar to La₄Ni₃O₁₀
  • 材料: Optimized structure
  • 方法: DFT+DMFT (eDMFT, WIEN₂K); CT-QMC solver at 290K
  • 观察: Outer-layer Co shows strong effective mass enhancement and non-Fermi liquid behavior; Inner-layer Ni is weakly correlated Fermi liquid
• Analysis of superconductivity indicators — La₄Co₂NiO₈Cl₂ is a promising candidate for high-temperature superconductivity
  • 材料: DFT+DMFT results
  • 方法: Self-energy analysis; Spectral functions; Local multiplet weights
  • 观察: Flat bands near Fermi level at M point; Orbital selectivity; Mixed high-spin and low-spin states