The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors^{1,2,3,4,5,6,7,8,9,10}. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO₂ (refs. ^11,12) has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO₂ and NdNiO₂, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with \(3d_{x^2-y^2}\) symmetry in the NiO₂ layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics^13,14,15, which are well known for heavy fermion behaviour, where the NiO₂ correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like ‘oxide-intermetallic’ replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.

继续寻找具有类似于铜酸盐高温超导体^{1,2,3,4,5,6,7,8,9,10}的电子特性的氧化镍基材料。最近在掺杂的无限层镍酸盐 NdNiO ₂中发现的超导性（参考文献^11,12）加强了这些努力。在这里，我们使用 X 射线光谱和密度泛函理论表明 LaNiO ₂和 NdNiO ₂的电子结构虽然与铜酸盐相似，但具有显着的区别。与铜酸盐不同，无限层镍酸盐中的稀土间隔层支持弱相互作用的三维 5 d金属态，它与NiO ₂层中具有\(3d_{x^2-y^2}\)对称性的准二维强相关态杂交。因此，无限层镍酸盐可被视为稀土金属间化合物^13,14,15的同胞，它们以重费米子行为而闻名，其中 NiO 2_相关层在稀土重费米子化合物。这种类似 Kondo 或 Anderson 晶格的“氧化物金属间化合物”取代了 Mott 绝缘体，成为掺杂后出现超导的参考状态。