orbital and itinerant electrons in infinite-layer nickelates*

The discovery of unconventional superconductivity in hole-doped NdNiO₂, similar to CaCuO₂, has received enormous attention. However, different from CaCuO₂, NdNiO₂ and LaNiO2 has itinerant electrons in the rare-earth spacer layer. Previous studies show that the hybridization between Ni-_{����2−��2} and rare-earth-d orbitals is very weak and thus RNiO₂ is still a promising analog of CaCuO₂. Here, we perform first-principles calculations to show that the hybridization between Ni-_{����2−��2} orbital and itinerant electrons in RNiO₂ are substantially stronger than previously thought. The dominant hybridization comes from an interstitial-s orbital rather than rare-earth-d orbitals, due to a large inter-cell hopping. Because of the hybridization, Ni local moment is screened by itinerant electrons, the antiferromagnetic fluctuation is suppressed and the critical U_Ni to stabilize a long-range magnetic ordering is increased. Our work shows that the electronic structure of RNiO₂ is distinct from CaCuO₂, implying that the observed superconductivity in infinite-layer nickelates does not emerge from a doped Mott insulator.