Model Construction and a Possibility of Cupratelike Pairing in a New d9 Nickelate Superconductor (Nd, Sr)NiO2

Effective models are constructed for a newly discovered superconductor (Nd, Sr) NiO2, which has been considered as a possible nickelate analog of the cuprates. Estimation of the effective interaction, which turns out to require a multiorbital model that takes account of all the orbitals involved on the Fermi surface, shows that the effective interactions are significantly larger than in the cuprates. A fluctuation exchange study suggests occurrence of dx2−y2-wave superconductivity, where the transition temperature should be lowered from the cuprates due to the larger interaction.