Magnetic, f-electron, and hole doping effects in infinite-layer nickelates

Recent discovery of superconductivity in the doped infinite-layer nickelates has renewed interest in understanding the nature of high-temperature superconductivity more generally. The low-energy electronic structure of the parent compound NdNiO₂, the role of electronic correlations in driving superconductivity, and the possible relationship between the cuprates and the nickelates are still open questions. Here, by comparing LaNiO₂ and NdNiO₂ systematically within a parameter-free, first-principles density-functional theory framework, we find the competition between the magnetically ordered phases depends mainly on the gaps in the Ni band. Our estimated value of the on-site Hubbard U in the nickelates is similar to that in the cuprates, but the value of the Hund’s coupling J_H is found to be sensitive to the Nd magnetic moment.  Moreover, taking LaNiO₂ as an example, we find the existence of intertwined low-energy phases with Van Hove singularities contributed by the Ni orbital in both undoped and doped nickelates, which could explain why there are no long-range magnetic orders in nickelates.  The hole doping effects are also discussed here. Our findings thus reveal the importance of fluctuating magnetic order in correlated materials.