Resolving where the density-wave gap opens in momentum space is essential for identifying the microscopic origin of the instability in layered nickelates. Using polarization-resolved electronic Raman scattering, we map the momentum selectivity of the spin-density-wave (SDW) gap in trilayer La4Ni3O10. We observe a SDW-induced redistribution of spectral weight on both the α pocket at the Brillouin-zone centre and a portion of the β pocket near the zone boundary, characterized by gap energies of approximately 55~meV. In contrast, no comparable spectral weight suppression is observed along the diagonal region of β pockets, implying little or no gap opening. This gap topology contrasts sharply with that in La3Ni2O7, where anisotropic SDW gaps open solely on the β pocket. Our results establish a distinct momentum-space gap topology between bilayer and trilayer nickelates, placing new constraints on the ordering wave vector and the mechanism of the density-wave instability relevant to superconductivity.
@article{arxiv.2602.02174,
title = {Contrasting Momentum-Selective Spin-Density-Wave Gaps in Bilayer and Trilayer Nickelates},
author = {Jun Shu and Jun Shen and Xiaoxiang Zhou and Yinghao Zhu and Qingsong Wang and Dengjing Wang and Weihong He and Jie Yuan and Kui Jin and Dawei Shen and Congcong Le and Jun Zhao and Zengyi Du and Ge He and Donglai Feng},
journal= {arXiv preprint arXiv:2602.02174},
year = {2026}
}