Daily Overview: Today’s highlight focuses on the theoretical identification of the superconducting pairing mechanism in the hybrid Ruddlesden-Popper nickelate La₃Ni₂O₇. Using mirror symmetry, the study proposes an orbital-selective diagonal gap test, demonstrating that a dz2-dominated pairing would introduce nodes along the diagonal direction of the Brillouin zone, contradicting the isotropic nodeless gap observed by ARPES and STM. In contrast, pairing dominated by the dx2-y2 orbital driven by Hund’s rule naturally yields a nodeless gap, consistent with experimental data. Weak-coupling calculations similarly favor dz2 domination, which is thus ruled out. This diagonal gap criterion firmly establishes that the Hund-driven dx2-y2 orbital pairing is the most relevant superconducting mechanism in La₃Ni₂O₇. arXiv submission processing window: 2026-08-06 00:00 to 2026-08-06 00:00 UTC.
1. Orbital-Selective Diagonal-Gap Test of Pairing in La$_3$Ni$_2$O$_7$
- Relevance Score:
5.5457 - Authors: Yu-Bo Liu, Zhi-Yan Shao, Zhiming Pan, Chen Lu, Fan Yang
- Link: https://arxiv.org/abs/2606.29470
- Paper page: What Does the Single-Particle Spectrum Imply on the Pairing Nature and Pairing Mechanism in La₃Ni₂O₇?
Summary: This paper proposes an orbital-selective diagonal energy gap test method utilizing mirror symmetry to determine the superconducting pairing mechanism in La₃Ni₂O₇. Owing to the vanishing hybridization between dx2-y2 and dz2 orbitals along the Brillouin zone diagonal, the gaps on the α/β and γ Fermi surfaces independently reflect the intrinsic pairing strengths of these two orbitals. Combined with the nodeless isotropic superconducting gap observed by ARPES and STM, if pairing is driven by a dz2-dominated hybridization mechanism, nodes or near-nodes would appear in the α/β pockets along the diagonal, contradicting experiments. Conversely, dx2-y2-dominated pairing driven by Hund’s rule yields an approximately isotropic nodeless gap, consistent with experimental data. Further RPA calculations indicate that weak-coupling theory tends to favor dz2-orbital dominance, also resulting in diagonal nodes and conflicting with observations. Consequently, this diagonal gap test establishes that Hund’s-rule-driven dx2-y2-orbital-dominated pairing is the most relevant pairing mechanism in La₃Ni₂O₇.