摘要
本研究利用偏振分辨拉曼散射并结合两轨道模型计算，揭示了三层镍酸盐La4Ni3O10密度波的多轨道特性。在声子部分，氧键伸缩模式在密度波转变温度T_DW附近出现明显的强度异常，而声子线形基本对称且频移和线宽变化微小，表明电子-声子耦合温和，密度波主要由电子不稳定性驱动而非晶格驱动。电子拉曼散射中，随着温度降低，连续谱权重在约114 meV（约910 cm-1）以下显著耗尽，并在该能量处出现一个偏振相关的尖锐峰，该峰在B2g通道中最强，B1g通道中几乎缺失。通过构建同时包含Ni-3dx2-y2和Ni-3d22轨道并在轨道空间中保留拉曼顶点的两轨道密度波态模型，计算确认该峰对应密度波能隙2Δ_DW，其打开表现为非相干和非平均场行为，且光谱响应必须依靠两个轨道的混合贡献，无法还原为任一单轨道投影。这些结果表明La4Ni3O10的密度波不稳定性具有本征的多轨道起源，为理解其与超导的竞争或共存关系提供了关键实验与理论依据。
材料
本批次暂无数据。
方法
本批次暂无数据。
关键词
本批次暂无数据。
亮点
本批次暂无数据。
结论
本批次暂无数据。
主要论断
- The density-wave energy gap in La4Ni3O10 is 2ΔDW = 114 meV, identified by a Raman peak at 910 cm-1.
- 证据: Observation of a pronounced peak at 910 cm-1 in electronic Raman scattering, strongly temperature- and polarization-dependent.,Model calculations reproduce the peak energy and polarization dependence when a DW potential is introduced.
- The Raman-active DW excitation has multiorbital character, requiring contributions from both Ni-3dx2-y2 and Ni-3d_z2 orbitals and their mixing.
- 证据: Single-orbital projections of the Raman vertex cannot reproduce the experimentally observed intensity ratio between B1g and B2g channels nor the linewidths.,Full orbital-matrix treatment of the Raman vertex yields agreement with experiment.
- The DW gap opens incoherently and exhibits non-mean-field behavior, with spectral weight depleting gradually and the 2ΔDW peak persisting above the transition temperature.
- 证据: Temperature-dependent Raman intensity shows gradual depletion of continuum spectral weight below 114 meV upon cooling, rather than a sharp gap edge.,The 910 cm-1 peak is observable above TDW, contrary to BCS mean-field expectations.
- Electron-phonon coupling is weak, and the DW is primarily driven by electronic instabilities rather than by lattice.
- 证据: Symmetric phonon lineshapes without Fano profiles indicate absence of strong electron-phonon coupling.,Phonon self-energy anomalies (frequency, linewidth) near TDW are subtle, consistent with weak coupling.
研究流程
- sample_preparation — High-qualityLa4Ni3O10 single crystals with a density-wave transition at ≈140 K were synthesized.
- 材料: La4Ni3O10 single crystals
- 方法: optical floating-zone method; post-annealing in oxygen; single-crystal X-ray diffraction; magnetic susceptibility measurements
- 观察: high-quality single crystals; phase purity confirmed (XRD, STEM); magnetic transition at 140K
- measurement — Raman spectra reveal phonon anomalies and an electronic excitation at 114 meV associated with the density-wave transition.
- 材料: La4Ni3O10 single crystal
- 方法: polarized Raman scattering; temperature-dependent spectroscopy
- 观察: phonon modes at 355, 400, 515 cm-1 show intensity anomalies across TDW; broad electronic continuum with spectral weight depletion up to 910 cm-1; prominent peak at 910 cm-1 (114 meV) strongest in B2g channel, nearly absent in B1g
- analysis — The 910 cm-1 peak corresponds to the density-wave gap 2ΔDW = 114 meV, and its multiorbital character is essential to explain the experimental spectra.
- 材料: DFT phonon calculations; minimal two-orbital model
- 方法: density-functional perturbation theory (DFPT); two-orbital Hubbard model with dx2-y2 and d_z2 orbitals; DW potential with ordering vector Q=(0.5π,0.5π); Raman response calculation with orbital-resolved vertices
- 观察: calculated phonon frequencies match experiment; model reproduces the 910 cm-1 peak and its polarization-dependent intensity; single-orbital projections fail to match the experimentally observed intensity ratio and linewidth
- interpretation — The density wave in La4Ni3O10 has a multiorbital origin involving both Ni-3dx2-y2 and Ni-3d_z2 states, with incoherent gap opening and dominant electronic-driving instability.
- 方法: comparison of model and experimental temperature dependencies; analysis of DW gap opening behavior
- 观察: spectral weight depletes gradually upon cooling, not a sharp onset; the DW peak persists above the transition temperature; symmetric phonon lineshapes indicate weak electron-phonon coupling