Abstract
The predominant Ni-multiorbital nature of infinite-layer neodynium nickelate at stoichiometry and with doping is revealed. We investigate the correlated electronic structure of NdNiO$_2$ at lower temperatures and show that first-principles many-body theory may account for Kondo(-lattice) features. Yet those are not only based on localized Ni-$d_{x^2-y^2}$ and a Nd-dominated self-doping band, but heavily builds on the participation of Ni-$d_{z^2}$ in a Hund-assisted manner. In a tailored three-orbital study, the half-filled regime of the former inplane Ni orbital remains surprisingly robust even for substantial hole doping $\delta$. Reconstructions of the interacting Fermi surface designate the superconducting region within the experimental phase diagram. They furthermore provide clues to recent Hall measurements as well as to the astounding weakly-insulating behavior at larger experimental $\delta$. Finally, a strong asymmetry between electron and hole doping, with a revival of Ni single-orbital features in the former case, is predicted. Superconductivity in Nd$_{1-x}$Sr$_x$NiO$_2$ is unlike the one in cuprates of distinct multiorbital kind, building up on nearly localized Ni-$d_{x^2-y^2}$ and itinerant Ni-$d_{z^2}$.
Highlights
The discovery of superconductivity in Sr-doped thin films of infinite-layer (IL) NdNiO2 with a Tc in the 10-K range marks a further milestone in the investigation of transition-metal oxides [1]
The third, highly debated question is most relevant for the superconducting mechanism, and it deals with the issue of deciding lowenergy physics based on single-Ni-orbital processes of the Ni-dx2−y2 kind [18,19,20,21,22,23] versus processes of the multi-Niorbital kind [7,9,10,11,31] at stoichiometry and with finite hole doping from replacing Nd by Sr
To proceed on the electronic states in IL nickelates in a more general and flexible way, let us turn to an explicit lowenergy description, where we focus on a minimal set of degrees of freedom that are essential for the key electronic processes at lower temperatures
Summary
The discovery of superconductivity in Sr-doped thin films of infinite-layer (IL) NdNiO2 with a Tc in the 10-K range marks a further milestone in the investigation of transition-metal oxides [1]. The third, highly debated question is most relevant for the superconducting mechanism, and it deals with the issue of deciding lowenergy physics based on single-Ni-orbital processes of the Ni-dx2−y2 kind [18,19,20,21,22,23] versus processes of the multi-Niorbital kind [7,9,10,11,31] at stoichiometry and with finite hole doping from replacing Nd by Sr. In a previous work [11], we focused on the one-toone comparison of IL nickelates with structurally akin cuprates. The present study uncovers crucial Ni-multiorbital mechanisms for Kondo physics at stoichiometry and for the accentuation of the superconducting region with hole doping. We compare hole doping with theoretical electron doping and detect a stronger single-orbital character of Ni-dx2−y2 flavor on the electron-doped side
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