Magnetic Correlations and Pairing Tendencies of the Hybrid Stacking Nickelate Superlattice La₇Ni₅O₁₇ (La₃Ni₂O₇/La₄Ni₃O₁₀) under Pressure

Motivated by the recent rapid progress in high-Tc nickelate superconductors, we comprehensively study the physical properties of the alternating bilayer trilayer stacking nickelate La₇Ni₅O₁₇. The high-symmetry phase of this material, without the tilting of oxygen octahedra, is not stable at ambient conditions but becomes stable under high pressure, where a small hole pocket γ₀, composed of the d3z²-r² states in the trilayer sublattice, appears. This pocket was identified in our previous work for trilayer La₄Ni₃O₁₀ as important to develop superconductivity. Moreover, using random-phase approximation calculations, we find a leading s^± pairing state for the high-symmetry phase under pressure with similar pairing strength as that obtained previously for the bilayer La₃Ni₂O₇ compound, suggesting a similar or higher superconducting transition temperature Tc. In addition, we find that the dominant magnetic fluctuations in the system driving this pairing state have antiferromagnetic structure both in-plane and between the planes of the top and bottom trilayer and bilayer sublattices, while the middle trilayer is magnetically decoupled.