来源 自动抓取
作者 Jun Zhan, Xianxin Wu, Jiangping Hu
arXiv / 出版方 https://arxiv.org/abs/2606.20533
PDF https://arxiv.org/pdf/2606.20533
相关度评分 4.499
主分类 cond-mat.supr-con
发布日期 2026-06-19
研究范式 理论研究
样品形态 未知

摘要

该研究采用多轨道巡游电子框架，结合 Hartree-Fock 和随机相近似方法，系统分析了双层与三层镍酸盐的磁基态及横模自旋激发。对于双层体系，虽双条纹序能量略低，但单条纹态的激发谱在波矢 Q_BL 处呈现各向异性低能锥形色散，在 Γ 点附近显示各向同性高能激发，与共振非弹性 X 射线散射及中子散射实验定性吻合；还发现 Q_BL 处的镜面偶数层间光学模能量与 Γ 处镜面奇数模一致。对于三层体系，镜面奇数和镜面偶数自旋密度波均可稳定，镜面奇数态能量更低，并携带由中间层主导的近零能隙模，而镜面偶数态仅含一支声学模和两支有能隙光学模；与实验对比支持镜面奇序图像。结果表明，磁激发可作为灵敏探针区分磁有序构型，并支撑多层镍酸盐磁性具有共同巡游起源的结论。

材料

方法

关键词

亮点

  • Identification of mirror-even optical interlayer modes at the ordering wavevector in bilayer nickelates, with energies matching those of mirror-odd modes at the zone center.
  • The mirror-odd spin-density-wave state in trilayer nickelates hosts an additional nearly gapless mode dominated by the middle layer, reflecting the absence of a static moment on that layer.
  • The single-stripe order in bilayer nickelates yields an anisotropic low-energy spin-wave cone and an isotropic high-energy ring around the Γ point, consistent with neutron scattering.
  • Calculated excitation spectra differentiate between competing magnetic configurations, providing a theoretical basis for experimental distinction.

结论

  • The excitation spectrum of the single-stripe state in bilayer nickelates is qualitatively consistent with RIXS and neutron scattering experiments, supporting the single-stripe magnetic order.
  • The mirror-odd spin-density-wave state is energetically favored over the mirror-even state in trilayer nickelates, and its excitation spectrum compares favorably with available RIXS data.
  • Magnetic excitation spectra serve as a sensitive probe to distinguish between magnetic ground states in multilayer nickelates.
  • The magnetism in bilayer and trilayer nickelates can be understood within a unified itinerant framework, where spin-density-wave order and superconductivity both originate from Fermi surface scattering between bands of opposite mirror parity.

主要论断

  • In bilayer nickelates, the single-stripe magnetic order, despite being slightly higher in energy, produces an excitation spectrum that qualitatively matches experimental RIXS and neutron scattering data.
    • 证据: the calculated excitation spectrum of the single-stripe state, characterized by an anisotropic low-energy cone at Q_BL and isotropic high-energy excitations near Γ, exhibits good qualitative agreement with recent RIXS and neutron scattering experiments (from abstract).,The observed slight gap feature around 25 meV at Q_BL can be captured in a magnetic configuration with a small φ, where the spinless site have a small moment (from full text).
  • For trilayer nickelates, the mirror-odd spin-density-wave state is energetically preferred and its excitation spectrum, featuring an additional nearly gapless middle-layer mode, is more consistent with RIXS data than the mirror-even state.
    • 证据: both mirror-odd and mirror-even spin-density-wave states can be stabilized near Q_TL, with the mirror-odd state lower in energy (from abstract).,Comparison with available RIXS data favors the mirror-odd spin-density-wave scenario (from abstract).,The mirror-odd SDW hosts an additional, nearly gapless mode dominated by the middle layer; the mirror-even SDW contains only one acoustic branch together with two gapped optical modes (from abstract).
  • Magnetic excitations provide a sensitive probe to identify the underlying magnetic order in multilayer nickelates and support a common itinerant origin for both magnetism and high-Tc superconductivity.
    • 证据: Our results show that magnetic excitations provide a sensitive probe of the magnetic order and support a common itinerant origin of magnetism in multilayer nickelates (from abstract).,Together with the itinerant pairing scenario driven by scattering between Fermi pockets of opposite mirror parity, our work supports a unified itinerant description (from conclusion).

研究流程

  • model_setup — The low-energy electronic structure supports magnetic instabilities driven by scattering between bands of opposite mirror parity.
    • 材料: Multi-orbital tight-binding Hamiltonian for bilayer and trilayer nickelates; Hubbard-Kanamori interaction parameters (U, J_H); Mirror-parity basis for electronic states
    • 方法: Construction of kinetic Hamiltonian with layer and orbital flavors; Onsite interactions written in particle-hole channel; Classification of bands by mirror parity
  • ground_state_determination — Hartree-Fock calculations show that the double-stripe order is favored in the bilayer, while the mirror-odd SDW is favored in the trilayer.
    • 材料: Hartree-Fock mean-field method; Spin-density-wave (SDW) order parameter ansatz with layer-dependent phase φ
    • 方法: Self-consistent solution of HF equations in folded Brillouin zone; Energy minimization over order parameter phase for bilayer and trilayer
    • 观察: Bilayer: double-stripe (φ≈π/2) has lower HF energy than single-stripe (φ=0); Trilayer: mirror-odd SDW is the robust ground state, with energy minimum at φ≈0 (single-stripe-like with spinless sites); Mirror-odd SDW has zero static moment on middle layer
  • excitation_spectra_calculation — The calculated spin excitation spectra reveal distinct signatures—number of gapless modes, optical branches, and anisotropy—that distinguish competing magnetic orders.
    • 材料: Transverse spin susceptibility within random phase approximation (RPA); Coherence factors from HF quasiparticle states; Projection operators onto layer-resolved and mirror-parity channels
    • 方法: Computation of bare particle-hole bubble using SDW-state vertices; RPA summation of ladder diagrams in the transverse spin channel; Spectral weight projection onto outer-layer mirror-odd/even and middle-layer channels
    • 观察: Bilayer SS: Gapless anisotropic cone at Q_BL, isotropic high-energy ring near Γ, mirror-even optical mode at Q_BL degenerate with mirror-odd at Γ; Bilayer DS: Additional downward feature along Γ-X, cone splitting near Q_BL, asymmetry along M-X; Trilayer mirror-odd: Two nearly gapless modes (outer-layer Goldstone and middle-layer soft mode) and one optical mode; Trilayer mirror-even: One gapless mode and two gapped optical modes near Q_TL
  • experimental_comparison_and_interpretation — The single-stripe order in bilayer and mirror-odd SDW in trilayer are the magnetic ground states consistent with experiments, supporting a unified itinerant picture for magnetism and superconductivity.
    • 材料: Reported RIXS spectra; Reported neutron scattering data
    • 方法: Qualitative comparison of low-energy ring anisotropy, high-energy ring isotropy, and optical modes
    • 观察: Bilayer SS excitations: anisotropic low-energy ring and isotropic high-energy ring match neutron scattering features; DS excitations are inconsistent; Trilayer mirror-odd: one optical mode consistent with RIXS; mirror-even would predict two optical modes; The mirror-odd SDW's nearly gapless middle-layer mode may be observable under pressure