Superconductivity in transition-metal oxides, akin to that found in high-temperature copper oxide materials (cuprates), has been sought for decades. After the recent finding of superconductivity in a special form of layered nickel oxides—namely, Sr-doped ${\mathrm{NdNiO}}_2$—that goal seemed finally reached. Here, we provide important insight into the correlated electronic structure of this nickel oxide system. As opposed to cuprates, where only a single copper orbital is key to understanding the correlated electronic structure, more than one orbital in nickel is crucial. Therefore, superconductivity in Sr-doped ${\mathrm{NdNiO}}_2$ is unlike that found in cuprates but instead is based on a novel and fascinating “multiorbital” mechanism in a strongly correlated electron system.

Our calculations clearly identify the superconducting region in the phase diagram as the one where this multiorbital character in nickel—found in the $\mathrm{Ni}(3d)$ shell—is strongest. We furthermore unveil the coupling between localized and itinerant electronic degrees of freedom in ${\mathrm{NdNiO}}_2$. By focusing on the three key orbitals that govern the dominant physics, we describe the effect of doping additional electrons or holes into the material. These results reproduce well the known experimental behavior with doping holes: the main transport properties and distinct phase behavior. The phase region that becomes superconducting at low temperatures is characterized in the normal state at higher temperatures as being built up by strongly localized electrons in one $\mathrm{Ni}(3d)$ orbital and itinerant ones in a second $\mathrm{Ni}(3d)$ orbital.

We predict that electron doping of ${\mathrm{NdNiO}}_2$ will lead to a stronger $\mathrm{Ni}(3d)$ single-orbital character—closer to cuprate characteristics—which could give rise to further novel physics.