Superconductivity in nickelate and cuprate superconductors with strong bilayer coupling

Abstract

The discovery of superconductivity at 80 K under high pressure in La3Ni2O7 presents the groundbreaking confirmation that high-Tc superconductivity is a property of strongly correlated materials beyond cuprates. We use density functional theory calculations of the band structure of La3Ni2O7 under pressure to verify that the low-energy bands are composed almost exclusively of Ni 3dx2−y2 and O 2p orbitals. We deduce that the Ni 3dz2 orbitals are essentially decoupled by the geometry of the high-pressure structure and by the effect of the Ni Hund coupling being strongly suppressed, which results from the enhanced interlayer antiferromagnetic interaction between 3dz2 orbitals and the strong intralayer hybridization of the 3dx2−y2 orbitals with O 2p. By introducing a tight-binding model for the Fermi surfaces and low-energy dispersions, we arrive at a bilayer t−t⊥−J model with strong interlayer hopping, which we show is a framework unifying La3Ni2O7 with cuprate materials possessing similar band structures, particularly the compounds La2CaCu2O6, Pb2Sr2YCu3O8, and EuSr2Cu2NbO8. We use a renormalized mean-field theory to show that these systems should have (d+is)-wave superconductivity, with a dominant d-wave component and the high Tc driven by the near-optimally doped β band, while the α band adds an s-wave component that should lead to clear experimental signatures.

Source-reported materials — not catalogue approval

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