Electronic structure, and magnetic and superconducting pairing tendencies of the alternating single layer–bilayer stacking nickelate La₅Ni₃O₁₁ under pressure

Nickelates have continued to surprise since their unconventional superconductivity was discovered. Recently, the layered nickelate La5Ni3O11 with hybrid single-layer and bilayer stacking showed superconductivity under high pressure. This compound combines features of single-layer La2NiO4 and bilayer La3Ni2O7, but its pairing mechanism remains to be understood. Motivated by this finding, here we report a comprehensive theoretical study of this system. Our density functional theory calculations reveal that the undistorted P4/mmm phase without pressure is unstable due to three distortion modes. As pressure increases, these modes are suppressed, leading to the high-symmetry P4/mmm phase without NiO6 octahedron tilting. Moreover, the “charge transfer” between the single-layer and bilayer sublattices was observed, leading to hole doping in the single-layer blocks. Our random-phase approximation calculations indicate a leading dx2−y2-wave pairing state that arises from spin-fluctuation scattering between Fermi surface states mainly originating from the single-layer blocks and additional weaker contributions from the bilayer blocks. These spin fluctuations could be detected by inelastic neutron scattering as a strong peak at q = (π,π). Our findings distinguish La5Ni3O11 from other nickelate superconductors discovered so far and the high-Tc cuprates. We also discuss both similarities and differences between La5Ni3O11 and other hybrid stacking nickelates.