Source capture
Authors Hiroshi Watanabe, Hirofumi Sakakibara, Kazuhiko Kuroki
arXiv / Publisher https://arxiv.org/abs/2603.13604
PDF https://arxiv.org/pdf/2603.13604
Relevance score 5.704
Primary category cond-mat.supr-con
Published 2026-03-17
Research paradigm Theoretical
Sample form Unknown

Summary

This study employs the variational Monte Carlo method to perform nonperturbative calculations on a bilayer two-orbital Hubbard model, revealing the hierarchical structure of superconducting pairing in the bilayer layered nickelate La3Ni2O7. It is found that the primary pairing interaction originates from the bonding-anti-bonding splitting of the Ni 3d(z2) orbital, while orbital hybridization redistributes superconducting correlations into the 3d(x2-y2) channel, despite its intrinsically weak pairing interaction. This distinction between the origin of pairing and the source of superconducting correlations explains why both orbital channels exhibit comparable long-range superconducting correlations, and the resulting s± state is robust against changes in Fermi surface topology, such as the disappearance of the α Fermi pocket. The results reconcile previously divergent theoretical perspectives on the pairing mechanism, indicating that the strength of superconducting correlations is primarily determined by the orbital character of the low-energy density of states, whereas the pairing interaction stems from orbital level splitting in the bilayer structure, highlighting the crucial role of orbital hybridization in stabilizing superconductivity in multilayer layered superconductors.

Materials

Methods

Keywords

  • hierarchical pairing structure
  • bonding antibonding splitting
  • orbital hybridization
  • s± wave superconductivity
  • orbital resolved density of states

Highlights

  • The study establishes a hierarchical structure: primary pairing from bonding-antibonding splitting and hybridization-induced correlations in other channels.
  • It reconciles apparently competing theoretical scenarios by distinguishing the origin of pairing from resulting correlations.

Conclusions

  • The primary pairing interaction originates from the bonding–antibonding splitting of the Ni 3dz2 orbitals.
  • Orbital hybridization redistributes superconducting correlations to the dx2-y2 channel despite its weak intrinsic pairing interaction.
  • The resulting s± state is robust against changes in Fermi-surface topology, including the disappearance of the α Fermi pocket.
  • Superconducting correlations are governed by the orbital character of the low-energy density of states.

Main claims

  • The primary pairing interaction originates from the bonding–antibonding splitting of the Ni 3dz2 orbitals.
    • Evidence: Abstract,Full text: The primary pairing interaction originates from the bonding–antibonding splitting of the Ni dz2 orbitals.
  • Orbital hybridization redistributes superconducting correlations to the dx2-y2 channel despite its weak intrinsic pairing interaction.
    • Evidence: Abstract,Full text: orbital hybridization redistributes superconducting correlations to the dx2-y2 channel despite its weak intrinsic pairing interaction.
  • The resulting s± state is robust against changes in Fermi-surface topology, such as the disappearance of the α pocket.
    • Evidence: Abstract,Full text: s± state is robust against changes in Fermi-surface topology.

Workflow

  • model_setup
    • Materials: La3Ni2O7
    • Methods: bilayer two-orbital Hubbard model; tight-binding parameters from DFT
  • variational_Monte_Carlo
    • Methods: Gutzwiller-Jastrow wave function; stochastic reconfiguration optimization
    • Observations: optimized gap parameters; long-range superconducting correlations
  • correlation_analysis
    • Methods: orbital-resolved density of states; gap structure in momentum space
    • Observations: comparable correlations in dz2 and dx2-y2 channels; gap structure robust to Fermi surface changes
  • interpretation — Primary pairing originates from bonding-antibonding splitting of dz2 orbitals; hybridization induces correlations in dx2-y2 channel.