Multiband d - p model and the electronic structure of quasi-two dimensional Nd1-x SrxNiO2

We study the tight-binding model of NiO2 planes in novel superconductors that takes into account anisotropic nickel-oxygen d - p hopping, oxygen-oxygen p - p hoppings, realistic crystal-field splittings, and the on-site Coulomb interactions {U, JH} both at nickel and oxygen ions. Electronic structure of the NiO2 layer is investigated for doping x = 0 and x = 0.25. For an ideal undoped system NdNiO2 (x = 0) we get robust Mott insulator and no magnetism as various magnetic ground states (ferromagnetic, C-type and G-type antiferromagnetic) have all the same energy. For self-doping x = 0.25 the system becomes conducting (zero HOMO-LUMO gap), with nonmagnetic ground state due to competing degenerate magnetic meta-stable states. These findings correlate well with experimental and theoretical data. However, it seems that the twro-dimensional model with p and d orbitals only is insufficient for a realistic description of Nd1-xSrxNiO2.