The realtionship of the electronic structure of Cuprate and Nickelate superconducting parent compounds

Ussing exact many body diagonalization (ED) methods and hybrid density functional band structure calculations (HSE) we compare the electronic structure of La3Ni2O7 in various magnetically ordered structures with the La2CuO4 in its known antiferromagnetic phase. We concentrate on the electronic structure of the Ni (Cu)O2 planes and the inter and intra plane interactions. We demonstrate that the NiO2 planes can be considered as very strongly hole doped CuO2 planes with the additional complication of Ni2+ in a spin 1 state while Cu2+ is spin 1/2 which strongly modifies and complicates the potential spin and charge density wave character of the ground state. As in the dope cuprates the extra holes beyond Ni2+ are mainly located on the in-plane O 2p orbitals strongly exchange coupled with neighboring Ni3d spins. The ED calculations suggest strong modifications from the HSE low energy scale electronic structure with strong quasi particle nature of the low energy scale states. ED suggests stabilizing particular HSE nearly degenerate phases. These spin 1/2 quasi particles resemble the spin 1/2 Zhang Rice or the Emery Reiter 3 spin polaron states of the cuprates. The spin 1/2 of is strongly delocalized over resulting a strongly weakened Neutron scattering amplitude. nt. Modeling the pressure dependence with model Hamiltonian parameters in the ED calculations we find a gradual change in the staggered nature of a charge and spin density wave state to a more uniform superconducting phase at elevated pressure. The pairing interactions could involve rather strong breathing mode phonons and effective attractive interactions between quasi particles.