Abstract
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, at the random-phase approximation level. 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.
