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${}_{3+\delta }$, we theoretically design an unconventional nickelate superconductor with $d^8$ 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${}_2$.

published version