Electronic structure, and magnetic and superconducting pairing tendencies of the alternating single layer–bilayer stacking nickelate La 5 Ni 3 O 11 under pressure
Nickelates have continued to surprise since their unconventional superconductivity was discovered. Recently, the layered nickelate La 5 Ni 3 O 11 with hybrid single-layer and bilayer stacking showed superconductivity under high pressure. This compound combines features of single-layer La 2 NiO 4 and bilayer La 3 Ni 2 O 7 , 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 NiO 6 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 𝑑 𝑥 2 −𝑦 2 -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 La 5 Ni 3 O 11 from other nickelate superconductors discovered so far and the high-𝑇 𝑐 cuprates. We also discuss both similarities and differences between La 5 Ni 3 O 11 and other hybrid stacking nickelates.