Contrasting Momentum-Selective Spin-Density-Wave Gaps in Bilayer and Trilayer Nickelates

Summary

Using polarization-resolved electronic Raman scattering, this study systematically maps the momentum-selective spin-density-wave (SDW) gap in the trilayer nickelate La₄Ni₃O₁₀. The experiments reveal that SDW-induced spectral weight redistribution occurs simultaneously on the α pocket at the Brillouin zone center and on part of the β pocket near the zone boundary, with a corresponding gap energy of approximately 55 meV, whereas no comparable spectral weight suppression is observed in the diagonal region of the β pocket, indicating that this region remains nearly gapless. This momentum-space gap topology contrasts sharply with that of the bilayer nickelate La₃Ni₂O₇, where only the β pocket exhibits an anisotropic SDW gap. These results establish distinct momentum-space gap topologies between bilayer and trilayer nickelates, providing new constraints on the ordering wave vector of the density-wave instability and the mechanism related to superconductivity.

Materials

• La₄Ni₃O₁₀

Methods

• polarization-resolved electronic Raman scattering

Keywords

• spin density wave gap
• momentum space gap topology
• α pocket
• β pocket

Highlights

• New constraints on ordering wave vector and density-wave mechanism relevant to superconductivity.

Conclusions

• In trilayer La₄Ni₃O₁₀, SDW gaps open on α pocket and part of β pocket, contrasting with La₃Ni₂O₇ where gaps only on β pocket, establishing distinct gap topology between bilayer and trilayer nickelates.

Main claims

• In La₄Ni₃O₁₀, SDW gaps open on both the α pocket and the β pocket near X/Y points, with gap energies approximately 55 meV.
  • Evidence: Raman spectra: A₁g channel shows spectral weight loss (α pocket), B₁g channel shows dip-hump structure (β pocket near X/Y).
• No significant gap opens on the diagonal region of β pockets in La₄Ni₃O₁₀.
  • Evidence: B₂g channel shows no change across T_SDW.
• The SDW gap topology is qualitatively different between La₄Ni₃O₁₀ and La₃Ni₂O₇.
  • Evidence: Direct comparison of Raman data: La₄Ni₃O₁₀ gaps on α and β near X/Y, La₃Ni₂O₇ gaps only on β with anisotropic coupling.

Workflow

• sample_growth — High-qualityLa₄Ni₃O₁₀ single crystals grown.
  • Materials: La₂O₃; NiO; oxygen
  • Methods: vertical optical-image floating-zone furnace
  • Observations: La₄Ni₃O₁₀ single crystals with DW transition near 140K
• Raman_spectroscopy — SDW-induced spectral weight redistribution observed in multiple channels.
  • Materials: single crystals
  • Methods: polarization-resolved Raman scattering; confocal geometry; 532 nm laser
  • Observations: Electronic continuum in all channels; Spectral weight loss below 1000 cm-1 in xx, x'x', x'y' channels below 140K; No change in xy channel
• symmetry_decomposition_and_analysis — Gaps open on α pocket and β pocket near X/Y points, but not on diagonal β pocket.
  • Methods: spectral decomposition into A₁g, B₁g, B₂g using pseudo-D₄h symmetry; difference spectra analysis
  • Observations: A₁g: dip below 800 cm-1 (gap on α pocket); B₁g: dip-hump crossing at 800 cm-1 (gap on β pocket near X/Y); B₂g: no change (no gap on diagonal β pocket); Gap energies: A₁g ≈56 meV, B₁g ≈55 meV
• comparison_with_bilayer — Distinct SDW gap topology between bilayer and trilayer nickelates.
  • Methods: comparison with La₃Ni₂O₇ Raman results
  • Observations: In La₄Ni₃O₁₀: gaps on α and β near X/Y; in La₃Ni₂O₇: gaps only on β with anisotropy; different coherence strength