Electronic structure of higher-order Ruddlesden Popper nickelates <i>R</i>_<i>n</i>+1Ni<i>_n</i>O_3<i>n</i>+1 (<i>R </i>= rare-earth, <i>n </i>= 4, 5, 6)

Layered nickelates have long been considered close analogs to cuprates and have been intensively investigated for their potential for superconductivity. The realization of this promise came last year, as NdNiO₂ was indeed shown to be superconducting upon hole doping. This material is obtained via topotactic reduction from its parent perovskite NdNiO₃ phase and is simply the infinite layer member of a larger structural series. In this context, analyzing the electronic properties of the yet unexplored parent Ruddlesden-Popper nickelate phases R_n+1Ni_nO_3n+1 (n=4-6) becomes important. Our systematic first-principles calculations in these materials reveal similarities and differences with cuprates in terms of their electronic structure. For example, large hole d_x²-y² Fermi surfaces that closely resemble the fermiology of optimally hole-doped cuprates are found, but they are accompanied by non-cuprate-like extra bands of primarily d_z² character.