来源 自动抓取
作者 Guan-Hao Feng, Jun Quan
arXiv / 出版方 https://arxiv.org/abs/2607.18094
PDF https://arxiv.org/pdf/2607.18094
相关度评分 5.576
主分类 cond-mat.supr-con
发布日期 2026-07-21
研究范式 理论研究
样品形态 薄膜

摘要

本文基于对称性唯象方法，结合电荷自洽密度泛函理论与动力学平均场理论，系统研究了杂化镍酸盐La5Ni3O11的低温物理与非常规配对机制。研究发现，单层子系统处于莫特绝缘态，超导电性主要源于双层子系统中Ni-e_g轨道。该体系呈现双能隙超导特征，主导配对来自dz2轨道间的层间耦合，次要配对来自dx2-y2轨道内的层内耦合。与高压下La3Ni2O7相比，La5Ni3O11中超导转变温度T_c的降低可归因于层间配对贡献的减弱，这直接反映在跃迁参数比值|tperp^z/tparallelx|的减小上。该统一图像为理解双层NiO2面内超导配对机制及γ口袋的作用提供了微观理论框架。

材料

方法

关键词

亮点

  • A phenomenological symmetry-based approach is developed to systematically analyze the low-energy physics and pairing symmetry in nickelates.
  • The monolayer subsystem of La5Ni3O11 is demonstrated to be Mott insulating, confining superconductivity to the bilayer subsystem.
  • Feasible symmetry-allowed pairing states are enumerated, revealing that sz2-wave interlayer pairing is the dominant instability, accompanied by a subdominant sx2+y2-wave intralayer pairing.
  • The suppressed Tc is quantitatively linked to the diminished interlayer hopping ratio, a trend consistent across bulk, thin-film, and hybrid nickelate superconductors.
  • The analysis suggests that enhancing the interlayer exchange while suppressing intralayer exchange may be an effective strategy to raise Tc.

结论

  • The superconductivity in La5Ni3O11 exhibits a two-gap nature, consisting of a leading interlayer pairing between the dz2 orbitals and a subleading intralayer pairing between the dx2-y2 orbitals.
  • The reduction of Tc in La5Ni3O11 compared to pressurized bulk La3Ni2O7 is attributed to the diminished contribution of the interlayer pairing, reflected by the decreased hopping parameter ratio |t⊥z/t∥x|.
  • The γ pocket is pivotal in stabilizing the s±-wave state through nesting with the β and α pockets, and its absence would suppress Tc.
  • The symmetry-based framework unifies the pairing mechanisms of La5Ni3O11 and La3Ni2O7, highlighting the role of the bilayer NiO2 planes in nickelate superconductors.

主要论断

  • The monolayer subsystem is Mott insulating and superconductivity originates from the bilayer subsystem.
    • 证据: The ML subsystem resides in a Mott insulating state; consequently, the correlated Fermi surface (FS) topology is strongly renormalized, leaving the low-energy physics dominated by the Ni-e_g orbitals of the BL subsystem.,the Ni1-dz2 orbital is fully Mott-insulated.
  • Superconductivity exhibits a two-gap nature with leading interlayer sz2-wave and subleading intralayer sx2+y2-wave pairings.
    • 证据: the superconductivity in La5Ni3O11 exhibits a two-gap nature, consisting of a leading interlayer pairing between the dz2 orbitals and a subleading intralayer pairing between the dx2-y2 orbitals.,Our results reveal that two-gap superconductivity occurs within the BL subsystem, reminiscent of pressurized La3Ni2O7.
  • The reduction of Tc compared to La3Ni2O7 is due to diminished contribution of interlayer pairing, reflected in the hopping ratio |t_perp^z/t_par^x|.
    • 证据: The reduction of Tc can be attributed to the diminished contribution of the interlayer pairing, as reflected by the hopping parameter ratio |tperp^z/tparallelx|.,the suppressed Tc in La5Ni3O11… The suppressed Tc thus reflects the diminished contribution of the interlayer pairing.

研究流程

  • electronic_structure_calculation — The low-energy physics is dominated by Ni-e_g orbitals of the bilayer subsystem; the monolayer is Mott insulating.
    • 材料: DFT; DMFT; cRPA; Wannier downfolding; TRIQS; maximum entropy method
    • 方法: charge self-consistent DFT+DMFT; Slater-Kanamori interaction with cRPA parameters; tight-binding model from Wannier downfolding; renormalization of band structures by DMFT self-energy
    • 观察: monolayer subsystem becomes Mott insulating; Ni1-dz2 orbital fully gapped; bilayer subsystem retains coherent quasiparticle features; renormalized FS shows three correlated pockets instead of five DFT pockets; interlayer hopping t_perp^z is reduced compared to La3Ni2O7
  • symmetry_analysis — A two-gap superconducting state with dominant interlayer sz2 pairing and subdominant intralayer sx2+y2 pairing is energetically favored.
    • 材料: group theory; p4/mmm layer group; Pauli matrices; BdG Hamiltonian
    • 方法: symmetry-allowed pairing matrix representations; classification into A1g, B1g, B2g, etc.; feasibility check using V < J ≈ 4|t|2/U; BCS condensation energy minimization
    • 观察: leading pairing is A1g interlayer sz2-wave between dz2 orbitals; subleading pairing is A1g intralayer sx2+y2-wave between dx2-y2 orbitals; two-gap coexistence lowers condensation energy vs single gap
  • superconducting_pairing_analysis — The leading sz2 pairing is stabilized by interband scattering involving the γ pocket; the subleading sx2+y2 pairing does not rely on the γ pocket.
    • 材料: RPA; linearized Eliashberg equation; BdG gap equations; projected gap functions
    • 方法: self-consistent gap equations; projected gap on FS pockets; RPA eigenvalue analysis
    • 观察: projected total gap exhibits s±-wave symmetry with accidental nodes on β pocket; V-shaped DOS consistent with tunneling spectra; RPA confirms s±-wave with nesting between γ and β/α pockets
  • pairing_mechanism_interpretation — The suppression of Tc is due to diminished interlayer pairing contribution, tracked by the hopping ratio |t_perp^z/t_par^x|; enhancing Jz alone is insufficient, requires suppressing Jx.
    • 材料: comparison of hopping ratios; pressure-dependent data
    • 方法: analysis of |t_perp^z/t_par^x| as control parameter
    • 观察: reduced Tc in La5Ni3O11 correlates with lower |t_perp^z/t_par^x|; in La3Ni2O7, |t_perp^z/t_par^x| decreases with pressure, matching Tc trend