Exchange interactions and sensitivity of the Ni two-hole spin state to Hund's coupling in doped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">NdNiO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>
Xiangang Wan, Vsevolod Ivanov, Giacomo Resta, I. Leonov, Sergey Y. Savrasov
Abstract
The discovery of superconductivity in Nd${}_{1\ensuremath{-}x}$Sr${}_{x}$NiO${}_{2}$ has resulted in a flurry of experimental and theoretical work to understand the nature of nickelate superconductivity as compared to that of the cuprates and pnictides. Here, the authors use a combination of LDA+U and linear-response methods to study the magnetic exchange interactions in Nd${}_{1\ensuremath{-}x}$Sr${}_{x}$NiO${}_{2}$. The analysis reveals an underlying Mott insulating state comprised of Ni-3${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$/Ni-3${d}_{{z}^{2}\ensuremath{-}{r}^{2}}$ orbitals with either an $S$=0 or $S$=1 two-hole ground state depending on the precise value of intra-atomic Hund's coupling.