Daily Overview: Today’s highlighted work focuses on an in-depth understanding of the electronic structure of mixed Ruddlesden–Popper nickelates. Using the bulk-sensitive Ni M1-edge s-core-level nonresonant inelastic X-ray scattering (s-NIXS) method, the study determined the angular distribution of Ni 3d holes in the ambient-pressure single-crystal bilayer nickelate La$_2$SmNi$_2$O$_7$; the fitted $e_g$ hole occupancy ratio is $h_z/h_x=0.94\pm0.06$, significantly higher than the 2/3 expected from the model of a fully occupied $d_{z^2}$ bonding band, close to the picture of approximately one hole per $e_g$ orbital under Hund coupling, and consistent with DMFT charge-transfer calculations for the high-pressure phase. The authors therefore argue that the superconducting pairing scenario for this material should allow both $e_g$ orbitals to participate in electron pairing, rather than being dominated solely by a single $d_{z^2}$ orbital; it should be noted that this is experimental support for the related pairing theory, not a direct establishment of the pairing mechanism. arXiv submission processing window: 2026-11-03 00:00 to 2026-11-03 00:00 UTC.
1. Direct imaging of the Ni $e_g$ hole orbitals in the bilayer nickelate La$_2$SmNi$_2$O$_7$
- Relevance Score:
5.2473 - Authors: Ethan Saïman, Feiyu Li, Junjie Zhang, Jean-Pascal Rueff, Victor Balédent
- Link: https://arxiv.org/abs/2611.01118
- Paper page: Direct imaging of the Ni e_g hole orbitals in the bilayer nickelate La₂SmNi₂O₇
Summary: This study used Ni M1-edge s-core-level nonresonant inelastic X-ray scattering (s-NIXS), a bulk-sensitive method, to determine the angular distribution of Ni 3d holes in the ambient-pressure single-crystal bilayer nickelate La2SmNi2O7. Fitting yielded an e_g hole occupancy ratio h_z/h_x = 0.94 ± 0.06, significantly higher than the 2/3 expected from the model of a fully occupied d_{z^2} bonding band and close to the picture of approximately one hole per e_g orbital under Hund coupling, and consistent with DMFT charge-transfer calculations for the high-pressure phase. On this basis, it is argued that the superconducting pairing scenario for this material should allow both e_g orbitals to participate in electron pairing rather than being dominated solely by a single d_{z^2} orbital; however, this constitutes experimental support for the relevant pairing theory and does not directly establish the pairing mechanism.