Prediction of several Co-based La₃Ni₂O₇-like superconducting materials

Summary

B_y electronic doping of the high-pressure bilayer cobaltate La₃Co₂O₇, cobalt-based La₃Ni₂O₇ analogs such as LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, and La₃Ni₂O₅Br₂ are predicted, which possess similar crystal structures and strongly correlated electronic states. Calculations based on density functional theory plus dynamical mean-field theory (DFT+DMFT) and random phase approximation (RPA) indicate that the cobalt 3d orbitals exhibit half-filled or near-half-filled occupancy, analogous to the nickel orbitals in La₃Ni₂O₇, and display strong Hund coupling and mass enhancement. The local magnetic moments (approximately 0.64 μ_B) of these cobalt-based compounds fall precisely within the optimal window for nickelate superconductivity (0.63–0.68 μ_B), strongly suggesting the possibility of high-temperature superconductivity via a similar spin fluctuation mechanism. RPA calculations further reveal that the leading pairing symmetry in electron-doped cobaltates is s-wave, belonging to the A₁ᵍ irreducible representation. This work provides a theoretical basis for achieving high-temperature superconductivity in cobalt-based systems and encourages further experimental synthesis and characterization.

Materials

• LaTh₂Co₂O₇
• La₃Ni₂O₅Cl₂
• La₃Ni₂O₅Br₂

Methods

• DFT+DMFT
• RPA
• tight-binding modeling

Keywords

• cobaltate superconductors
• hund's coupling
• s wave pairing
• electron doping

Highlights

• First prediction of La₃Ni₂O₇-like high-temperature superconductivity in cobalt-based materials.
• Shows that electron doping of La₃Co₂O₇ can achieve electronic structure similar to La₃Ni₂O₇.
• Provides theoretical basis for experimental synthesis of new cobaltate superconductors.

Conclusions

• Electron-doped bilayer cobaltates (LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, La₃Ni₂O₅Br₂) are predicted to be strongly correlated analogs of La₃Ni₂O₇.
• Co 3d orbitals are half-filled or near-half-filled, exhibiting strong Hund coupling and mass enhancement.
• Local magnetic moments (0.64 μB) fall within the optimal window for nickelate superconductivity.
• RPA calculations reveal s-wave as the leading pairing symmetry (A₁g representation).

Main claims

• Co-based La₃Ni₂O₇ analogs (LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, La₃Ni₂O₅Br₂) exhibit similar crystal structures and strongly correlated electronic states
  • Evidence: From abstract: 'Electron doping of the high-pressure bilayer cobaltate La₃Co₂O₇ yields LaTh₂Co₂O₇, La₃Ni₂O₅Cl₂, and La₃Ni₂O₅Br₂, which exhibit closely related crystal structures and strongly correlated electronic states'
• Random-phase-approximation calculations reveal s-wave as the leading pairing symmetry in these compounds
  • Evidence: From abstract: 'Random-phase-approximation calculations reveal s-wave as the leading pairing symmetry in these compounds'
• Local magnetic moments (0.64 μ_B) fall within the optimal window for nickelate superconductivity (0.63-0.68 μ_B)
  • Evidence: From text: 'local magnetic moments we calculate for these cobalt-based compounds—ranging from 0.637 to 0.647—fall precisely within the narrow window (0.63–0.68) recently identified as optimal for high-T_c superconductivity'

Workflow

• density_functional_theory_calculations — Co-based compounds isostructural to La₃Ni₂O₇
  • Materials: La₃Co₂O₇; LaTh₂Co₂O₇; La₃Ni₂O₅Cl₂; La₃Ni₂O₅Br₂
  • Methods: DFT with PBE functional; structural optimization
  • Observations: crystal structures; band structures
• dynamical_mean_field_theory_calculations — Co compounds exhibit strong correlations similar to La₃Ni₂O₇
  • Materials: Optimized structures
  • Methods: DFT+DMFT
  • Observations: spectral function; self-energy; local moments
• random_phase_approximation_analysis — s-wave is leading pairing symmetry in electron-doped cobaltates
  • Materials: Tight-binding models from DFT
  • Methods: RPA for pairing symmetry
  • Observations: leading pairing eigenvalues; gap symmetry