Designing nickelate superconductors with d8 configuration exploiting mixed-anion strategy

Abstract

Inspired by a recently proposed superconducting mechanism for a new cuprate superconductor Ba2CuO3+δ, we theoretically design an unconventional nickelate superconductor with a d8 electron configuration. Our strategy is to enlarge the on-site energy difference between 3dx2-y2 and other 3d orbitals by adopting halogens or hydrogen as out-of-plane anions, so that the 3d bands other than dx-y2 lie just below the Fermi level for the d8 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)NiO2.