Superconductivity and magnetism in bilayer nickelates: itinerant perspective

摘要

该研究从巡游视角探讨了双层镍氧化物的超导与磁性。基于对压缩应变薄膜角分辨光电子能谱的紧束缚拟合，作者引入了标准在位排斥相互作用（包括轨道内U、轨道间U′、Hund耦合JH和配对跳跃JP），并通过随机相位近似（RPA）考虑粒子-空穴涨落对这些裸相互作用进行重整，从而得到有效配对相互作用。结果表明，在强Hund耦合区域，s波超导和(π/2, π/2)自旋密度波（SDW）有序是优势基态；而在弱Hund耦合下，d波配对和(π, π)自旋密度波成为主导基态。该结果与先前密度矩阵重正化群（DMRG）研究定性一致，强调了Hund耦合在决定体系超导配对对称性和磁性类型中的关键作用。

材料

• La₃Ni₂O₇

方法

• tight binding
• random phase approximation (RPA)
• ARPES

关键词

• s wave superconductivity
• d wave superconductivity
• spin density wave
• hund's coupling

亮点

• Ke_y role of Hund's coupling in determining nature of superconductivity and magnetism.
• Qualitative consistency with DMRG studies.

结论

• In strong Hund's coupling regime, s-wave superconductivity and (π/2,π/2) SDW order are favored; in weak Hund's coupling, d-wave pairing and (π,π) SDW are leading.

主要论断

• Strong Hund's coupling favors s-wave superconductivity and (π/2,π/2) SDW order; weaker Hund's coupling favors d-wave pairing and (π,π) SDW
  • 证据: From abstract: 'In the strong Hund's coupling regime, we find that s-wave superconductivity and (π/2,π/2) SDW order are the favored ground states. With weaker Hund's coupling, we find that d-wave pairing and (π,π) SDW are the leading ground states'
• Results are qualitatively consistent with DMRG studies, highlighting key role of Hund's coupling
  • 证据: From abstract: 'Our results are qualitatively consistent with earlier DMRG studies, and point to the key role played by Hund's coupling'

研究流程

• model_construction — Two-orbital model with Hund's coupling captures low-energy physics
  • 材料: La₃Ni₂O₇ compressively strained thin film
  • 方法: tight-binding fit to ARPES data
  • 观察: Fermi surface with α and β pockets
• random_phase_approximation_calculations — Strong JH favors s-wave SC and (π/2,π/2) SDW; weak JH favors d-wave and (π,π) SDW
  • 材料: Tight-binding model
  • 方法: RPA for spin susceptibility and effective pairing interaction
  • 观察: leading pairing eigenvalue; gap symmetry; spin susceptibility
• analysis_of_pairing_symmetry_and_magnetism — Hzund's coupling is key determinant of both pairing and magnetic order
  • 材料: RPA results
  • 方法: Linearized gap equation; Susceptibility peak analysis
  • 观察: Phase diagram of pairing symmetry; Magnetic ordering vectors