A substantial hybridization between correlated Ni-d orbital and itinerant electrons in infinite-layer nickelates

TL;DR

This study reveals a strong hybridization between Ni-dx2-y2 orbitals and itinerant electrons in RNiO2, challenging previous assumptions and suggesting a different mechanism for superconductivity than in cuprates.

Contribution

First-principles calculations show that hybridization in RNiO2 is stronger than previously thought, involving interstitial-s orbitals, altering the understanding of its electronic structure.

Findings

Hybridization between Ni-dx2-y2 and itinerant electrons is substantial.

The dominant hybridization involves interstitial-s orbitals, not rare-earth-d orbitals.

Ni local moments are screened, and the critical U for magnetic order is increased.

Abstract

The discovery of unconventional superconductivity in hole doped NdNiO2, similar to CaCuO2, has received enormous attention. However, different from CaCuO2, RNiO2 (R = Nd, La) has itinerant electrons in the rare-earth spacer layer. Previous studies show that the hybridization between Ni-dx2-y2 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-dx2-y2 orbital and itinerant electrons in RNiO2 is 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 and the critical U_Ni for 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.