Designing nickelate superconductors with d^{8} configuration exploiting mixed-anion strategy

Abstract

Inspired by a recently proposed superconducting mechanism for a new cuprate superconductor Ba_{2}CuO_{3+δ}, we theoretically design an unconventional nickelate superconductor with a d^{8} electron configuration. Our strategy is to enlarge the on-site energy difference between 3d_{x^{2}−y^{2}} and other 3d orbitals by adopting halogens or hydrogen as out-of-plane anions, so that the 3d bands other than d_{x^{−}y^{2}} lie just below the Fermi level for the d^{8} configuration, acting as incipient bands that enhance superconductivity. We also discuss a possible relevance of the present proposal to the recently discovered superconductor (Nd,Sr)NiO_{2}.