来源 自动抓取
作者 Huimei Liu, Giniyat Khaliullin
arXiv / 出版方 https://arxiv.org/abs/2602.23989
PDF https://arxiv.org/pdf/2602.23989
相关度评分 5.218
主分类 cond-mat.str-el
发布日期 2026-03-24
研究范式 理论研究
样品形态 未知

摘要

该研究构建了双层镍氧化物超导能隙结构的微观理论模型，模型中dx2-y2对称性的传导带与局域化的d3z2-r2自旋共存。强层间耦合使局域磁矩形成单重态基态，其虚拟的单重态-三重态激发（即“triplon”）介导了传导电子间的配对相互作用，由此产生带间s±波配对，两个能带（α和β）上的序参量符号相反。理论结果自然解释了实验中观测到的关键特征：尽管α带态密度较小，但其超导能隙更大，且能隙呈现出由非局域Kondo耦合导致的显著动量空间各向异性。这些发现有力支持了triplon介导的配对机制作为双层镍氧化物超导的微观起源。

材料

方法

关键词

亮点

  • Provides a microscopic mechanism for the observed gap hierarchy in bilayer nickelates.
  • Triplon-mediated pairing naturally accounts for key features seen in STM and ARPES.
  • Offers resolution to the debate on pairing mechanism in bilayer nickelates.

结论

  • Strong interlayer coupling drives local moments into a singlet ground state; virtual singlet-triplet excitations (triplons) mediate pairing.
  • This yields interband s±-wave pairing with opposite signs on the α and β bands.
  • The theory explains the larger gap on the α band despite its smaller DOS, and pronounced gap anisotropy from nonlocal Kondo coupling.
  • The calculated tunneling spectra reproduce experimental two-gap features.

主要论断

  • Triplon-mediated pairing yields interband s±-wave superconductivity with larger gap on α band despite smaller density of states
    • 证据: From abstract: 'This yields interband s± pairing, with opposite signs of the order parameter on the two (α and β) bands. Our theory naturally explains the key experimental features: a larger gap on the α band despite its smaller density of states'
  • Pronounced gap anisotropy arises from nonlocal Kondo coupling
    • 证据: From abstract: 'pronounced gap anisotropy arising from nonlocal Kondo coupling'
  • Results support triplon-mediated pairing as microscopic origin of superconductivity in bilayer nickelates
    • 证据: From abstract: 'The results support triplon-mediated pairing as the microscopic origin of superconductivity in bilayer nickelates'

研究流程

  • model_construction — Localized dz2 spins form interlayer singlet ground state; triplon excitations mediate pairing
    • 材料: Bilayer nickelate films
    • 方法: Tight-binding model for dx2-y2 and dz2 orbitals; Triplon theory for local spins
    • 观察: Band dispersions; Fermi surface with α and β bands
  • bcs_mean_field_analysis — Interband s±-wave pairing with larger gap on α band despite smaller DOS
    • 材料: Effective pairing Hamiltonian from triplon exchange
    • 方法: BCS mean-field theory
    • 观察: Superconducting gaps on α and β bands; Gap anisotropy
  • comparison_with_experiment — Theory reproduces experimental STM spectra
    • 材料: Calculated gaps
    • 方法: Simulation of tunneling spectra
    • 观察: Two-gap structure in spectra