Detecting pairing symmetry of bilayer nickelates using electronic Raman scattering

摘要

本研究利用双轨道双层模型，通过多轨道和能带加和两种方法系统计算了不同拉曼通道下的电子拉曼响应，以区分双层镍酸盐超导体La₃Ni₂O₇中争议的配对对称性。通过对比多轨道与能带加和近似的拉曼磁化率，发现拉曼响应能有效区分不同配对对称性，并识别完全开缝和节状超导态中依赖于费米口袋的能隙大小。具体地，节状d_x^2-_y²/d_xy波配对在低能下表现出稳健的幂律行为，与完全开缝配对截然不同；而对于s±波配对，则可以确定β口袋上的能隙各向异性细节。研究还强调了多轨道效应对拉曼谱的关键塑造作用，并指出电子拉曼散射作为一种具有对称分辨能力的探针，能够为确定非常规超导体的超导能隙结构提供有力手段，对理解双层镍酸盐的超导机制具有重要实验意义。

材料

• La₃Ni₂O₇ (bilayer nickelate)

方法

• Electronic Raman scattering formalism
• Multiorbital approach
• Band-additive approach

关键词

• pairing symmetry
• raman response
• superconducting gap
• multiorbital effects
• power law behavior

亮点

• Our results highlight the crucial role of multiorbital effects in shaping the Raman spectra.
• Electronic Raman scattering is established as a powerful and symmetry-resolved probe for determining the superconducting gap in unconventional superconductors.

结论

• Nodal d-wave pairing exhibits robust power-law behavior at low energies, distinctly different from fully gapped pairing.
• For s±-wave pairing, detailed gap anisotropy on the β pocket can be resolved.
• Raman response can effectively differentiate various pairing symmetries and identify Fermi-pocket-dependent gap sizes.

主要论断

• Electronic Raman scattering can effectively distinguish different pairing symmetries in bilayer nickelates, with nodal d-wave pairing showing robust power-law behavior distinct from fully gapped s±-wave pairing.
  • 证据: Abstract: 'nodal d-wave pairing exhibits robust power-law behavior at low energies, distinctly different from fully gapped pairing; for s±-wave pairing, detailed gap anisotropy on the β pocket can be determined'
• Multiorbital effects play a crucial role in shaping the Raman spectra, and the approach provides a powerful symmetry-resolved probe for the superconducting gap.
  • 证据: Abstract: 'the study emphasizes the crucial role of multiorbital effects in shaping the Raman spectra, and points out that electronic Raman scattering… provides a powerful means to determine the superconducting gap structure'

研究流程

• Model construction
  • 材料: Bilayer nickelate La₃Ni₂O₇
  • 方法: Two-orbital bilayer tight-binding model; Various pairing symmetries (s±, d-wave)
  • 观察: Three Fermi pockets: α, β, γ
• Raman response calculations — Electronic Raman scattering can distinguish pairing symmetries in bilayer nickelates
  • 材料: Model with superconducting order parameters
  • 方法: Multiorbital and band-additive Raman susceptibility; Effective mass approximation for Raman vertices
  • 观察: Distinct low-energy power-law behaviors for nodal vs fully gapped pairings; Gap anisotropy on β pocket detectable