Correlation-Driven Orbital-Selective Fermiology and Superconductivity in the Bilayer Nickelate La₃Ni₂O₇

Summary

Based on the bilayer two-orbital Hubbard model, this study systematically investigates the effects of electronic correlations on the Fermi surface topology and superconducting pairing symmetry in La₃Ni₂O₇ using the time-dependent variational principle cluster perturbation theory (TDVP-CPT) and large-scale density matrix renormalization group (DMRG) methods. TDVP-CPT calculations on clusters containing up to 16 physical sites reveal that electronic correlations drive significant orbital-selective low-energy spectral reconstruction: the spectral weight of the dz² orbital is progressively depleted, the γ band sinks below the Fermi level, while the α and β bands exhibit a pseudogap, ultimately leading to the formation of a Fermi arc dominated by the dx²-y² orbital in the strong-coupling regime. DMRG calculations further demonstrate that the dominant superconducting pairing correlations evolve consistently with this Fermi surface reconstruction, transitioning from interlayer spin singlet pairing mediated primarily by the dz² orbital in the weak-coupling regime to pairing dominated by the dx²-y² orbital in the strong-coupling regime, while maintaining s±-wave symmetry throughout. The study indicates that the disappearance of the γ Fermi surface does not suppress superconductivity but instead signifies a correlation-driven change in the pairing channel, with key intermediate mechanisms including interlayer antiferromagnetic fluctuations, Hund coupling, and interorbital hybridization.

Materials

• La₃Ni₂O₇

Methods

• Time-dependent variational principle cluster perturbation theory (TDVP-CPT)
• Density matrix renormalization group (DMRG)

Keywords

• orbital selective reconstruction
• fermi arcs
• pseudogap
• s± wave pairing
• interlayer antiferromagnetism
• hund's coupling
• inter orbital hybridization
• lifshitz transition

Highlights

• Large-scale TDVP-CPT calculations on clusters up to 16 physical sites, the largest such study for this system.
• Correlation-driven pairing channel shift demonstrates that the pairing mechanism is highly regime-dependent, with Hund's coupling and inter-orbital hybridization playing key roles at strong coupling.

Conclusions

• Electronic correlations drive an orbital-selective reconstruction: the dz2-derived γ band sinks below the Fermi level, pseudogaps open on α and β bands, leading to dx2-y2-dominated Fermi arcs at strong coupling.
• The dominant superconducting pairing correlations shift from dz2-dominated to dx2-y2-dominated interlayer spin-singlet pairing while retaining s± structure.
• Disappearance of the γ pocket does not suppress superconductivity; it signals a correlation-driven shift of the pairing channel mediated by interlayer antiferromagnetism, Hund's coupling, and inter-orbital hybridization.

Main claims

• Electronic correlations drive an orbital-selective reconstruction: d_z² spectral weight is depleted, γ band sinks below Fermi level, and pseudogaps open on α and β bands, resulting in dx²-y²-dominated Fermi arcs at strong coupling.
  • Evidence: TDVP-CPT spectral functions show progressive depletion of d_z² weight with increasing U; Fermi arcs emerge at U=6.0 eV
• The leading superconducting correlations transition from d_z²-dominated to dx²-y²-dominated interlayer spin-singlet pairing as correlations increase, while retaining s± structure.
  • Evidence: DMRG calculations show pairing correlation exponent K decreases for dx²-y² and increases for d_z² with increasing U; interlayer pairing remains algebraic
• At weak coupling, inter-orbital hybridization drives d_z² pairing; at strong coupling, both Hund's coupling and inter-orbital hybridization are essential for dx²-y² pairing.
  • Evidence: DMRG with varied J_H and hybridization shows different dependencies in weak and strong coupling regimes; simultaneous suppression of both greatly weakens pairing

Workflow

• model_definition — Realistic multi-orbital model for La₃Ni₂O₇.
  • Materials: La₃Ni₂O₇ tight-binding parameters from literature
  • Methods: bilayer two-orbital Hubbard model with on-site interactions
  • Observations: model captures orbital-selective correlation effects
• tdvp_cpt_spectral_calculations — Electronic correlations drive Fermi surface reconstruction.
  • Materials: clusters up to 16 physical sites
  • Methods: time-dependent variational principle based cluster perturbation theory
  • Observations: orbital-selective depletion of d_z² spectral weight; γ band sinks below Fermi level; pseudogaps on α and β bands
• dmrg_superconducting_correlations — Leading superconducting correlations shift from d_z² to dx²-y² with increasing correlation strength.
  • Materials: L×W lattices (W=2,4)
  • Methods: density matrix renormalization group with bond dimension up to 12000
  • Observations: interlayer pairing correlations decay algebraically; transition from d_z²- to dx²-y²-dominated pairing
• analysis_of_pairing_mechanism — Microscopic pairing mechanism is regime dependent.
  • Materials: DMRG results with varying J_H and hybridization
  • Methods: systematic variation of interaction parameters
  • Observations: at weak coupling, inter-orbital hybridization drives d_z² pairing; at strong coupling, both Hund's coupling and hybridization are essential for dx²-y² pairing