Electronically Inactive Intercalated La₂NiO₄Layer in Superconducting La₅Ni₃O₁₁

Summary

This study systematically investigates the electronic role of the intercalated La₂NiO₄ (214) layer in the superconducting material La₅Ni₃O₁₁ by combining density functional theory, Wannier tight-binding modeling, and rotationally invariant slave-boson calculations. A two-orbital model is constructed for the embedded 214 layer using realistic electronic parameters extracted from PBE and HSE₀₆ functionals, and its correlated ground-state phase diagram is computed via the slave-boson approach. The results reveal that within realistic ranges of crystal-field splitting and Coulomb interaction, this layer tends to reside in an antiferromagnetic insulating state or a band insulating state rather than a paramagnetic metallic state, with its low-energy spectral weight completely suppressed. Further analysis of a coupled model incorporating the La₃Ni₂O₇ (327) block and the 214 layer shows that interlayer hybridization does not restore any effective density of states originating from the 214 layer near the Fermi level. Consequently, the low-energy electronic structure of La₅Ni₃O₁₁ is dominated by the 327 block, while the intercalated 214 layer remains electronically inert and does not contribute to the formation of the Fermi surface. This finding clarifies the minimal low-energy effective model for this mixed-layer nickelate and offers a unified picture for understanding superconductivity in intercalated Ruddlesden-Popper nickelates.

Materials

• La₅Ni₃O₁₁
• La₂NiO₄
• La₃Ni₂O₇

Methods

• DFT
• Wannier-based tight-binding modeling
• rotationally invariant slave-boson method
• Gutzwiller approximation

Keywords

• electronically inactive
• ruddlesden popper nickelates
• two orbital model
• jahn teller splitting
• antiferromagnetic insulator
• band insulator
• low energy electronic structure
• intercalated layer

Highlights

• The intercalated La₂NiO₄ layer is found to be electronically inactive, challenging the expectation of additional Fermi pockets from the hybrid structure.
• Both PBE and HSE₀₆ functional parametrizations independently lead to the same conclusion of electronic inactivity despite favoring different insulating mechanisms.
• Interlayer hybridization does not reactivate the 214 layer; the Fermi surface remains dominated by the 327 block.
• La₅Ni₃O₁₁ can be viewed as a quasi-two-dimensional 327 system with an electronically inert spacer, analogous to intercalated FeSe superconductors.

Conclusions

• The intercalated La₂NiO₄ layer in La₅Ni₃O₁₁ is electronically inactive at low energies, residing in gapped insulating states rather than a paramagnetic metallic state.
• Neither PBE- nor HSE₀₆-derived parameters place the embedded 214 layer in a metallic regime; both lead to insulating behavior (AFM or band insulator).
• Interlayer hybridization between the 327 and 214 blocks fails to generate any 214-derived spectral weight at the Fermi level.
• The low-energy electronic structure of La₅Ni₃O₁₁ is governed primarily by the La₃Ni₂O₇ block, making the system effectively a quasi-two-dimensional 327 electronic system.
• This establishes a minimal low-energy model for La₅Ni₃O₁₁ and provides a unified framework for understanding superconductivity in intercalated Ruddlesden-Popper nickelates.

Main claims

• Realistic electronic parameters place the intercalated La₂NiO₄ layer in gapped insulating regimes (AFM or BI) rather than a paramagnetic metallic state.
  • Evidence: PBE and HSE₀₆ parametrizations from DFT show that at U≈3-4 eV, the 214 layer is either in a high-spin AFM insulating state (PBE) or a band insulating state (HSE₀₆),RISB phase diagram (Fig. 2) confirms gapped phases.
• Interlayer hybridization with the La₃Ni₂O₇ block fails to generate appreciable La₂NiO₄-derived spectral weight at the Fermi level.
  • Evidence: Coupled model band structure (Fig. 3) shows bands at EF are predominantly 327-derived, no additional 214-derived Fermi pockets.
• The low-energy electronic structure of La₅Ni₃O₁₁ is governed primarily by the La₃Ni₂O₇ block, with the intercalated La₂NiO₄ layer electronically inactive.
  • Evidence: Abstract: 'Our results demonstrate that the low-energy electronic structure of La₅Ni₃O₁₁ is governed primarily by the La₃Ni₂O₇ block, with the intercalated La₂NiO₄ layer remaining electronically inactive.',Coupled model results and phase diagram.
• This establishes a minimal low-energy description of La₅Ni₃O₁₁ and provides a unified framework for understanding superconductivity in intercalated Ruddlesden–Popper nickelates.
  • Evidence: Abstract: 'This establishes a minimal low-energy description of La₅Ni₃O₁₁ and provides a unified framework for understanding superconductivity in intercalated Ruddlesden–Popper nickelates.'

Workflow

• model_construction — A minimal low-energy model describes the 214 layer and its coupling to the 327 block.
  • Materials: La₅Ni₃O₁₁ crystal structure; two-orbital tight-binding model for intercalated La₂NiO₄ layer; minimal coupled 327+214 model; Ni dx2-y2 and dz2 orbitals
  • Methods: tight-binding modeling; construction of hopping Hamiltonian including in-plane and interlayer terms
• parameter_extraction — A broad range of Jahn-Teller splittings is spanned, capturing the sensitivity to the exchange-correlation functional.
  • Materials: VASP with PAW method; PBE and HSE₀₆ exchange-correlation functionals; Wannier90
  • Methods: density functional theory (DFT); Wannierization to obtain tight-binding parameters
  • Observations: PBE yields Δ_JT = 0.5571 eV; HSE₀₆ yields Δ_JT = 2.5341 eV; hopping amplitudes differ by tens of meV
• correlated_calculation — Realistic parameters place the isolated 214 layer in gapped insulating states, not paramagnetic metal.
  • Materials: two-orbital Hubbard model with local Coulomb U, Hund's JH=0.1U; RISB formalism
  • Methods: rotationally invariant slave-boson method at saddle-point level; evaluation of paramagnetic metal (PM), antiferromagnetic (AFM), and band insulating (BI) solutions
  • Observations: phase diagram: for U=3-4 eV, PBE parameters (small Δ_JT) give AFM (high-spin S=1, M=1.88 μB); HSE₀₆ parameters (large Δ_JT) give BI (orbital-polarized, nonmagnetic)
• coupled_layer_analysis — Interlayer hybridization does not reactivate the 214 layer; its spectral weight remains negligible at EF.
  • Materials: effective Hamiltonian H_eff5311 = H₃₂₇ + H₂₁₄ + H_hyb; interlayer hopping amplitude t_perp^zz = -0.0237 eV
  • Methods: RISB solution of coupled model, paramagnetic for 327 block
  • Observations: layer-resolved band structure: Fermi-level bands are predominantly 327-derived; no additional 214-derived Fermi-surface pocket appears; 214 bands separated from EF
• interpretation — The low-energy physics of La₅Ni₃O₁₁ is governed by the La₃Ni₂O₇ block; the intercalated La₂NiO₄ layer is electronically inactive, making the system effectively a quasi-2D 327 electronic system.
  • Methods: analysis of results and comparison with experiment
  • Observations: similar phenomenology of La₅Ni₃O₁₁ and La₃Ni₂O₇ under pressure; recent ARPES on thin films shows no extra 214 pockets