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A piece of metal is cooled to minus two hundred degrees, and electric current begins to flow through it without the slightest friction, like water in a pipe flowing without touching the walls. This behavior is called superconductivity. For a long time, it was sought in nickelates — compounds of nickel and oxygen, structurally similar to the famous cuprate superconductors. It was believed that to trigger superconductivity, one had to replace some atoms in the crystal with others — about every fifth atom. That would be like requiring the ice rink to be sprinkled with sand before skates could glide.

In the new work, physicists grew ultra-thin films of the nickelate PrNiO₂, so thin that their thickness is comparable to the size of a few atoms. And they found superconductivity in a completely pure substance, without any additives. The films carried current without resistance and expelled magnetic fields — the two main signatures of true superconductivity. To rule out any influence from the substrate on which the films were grown, the scientists created a complex layered structure, and confirmed that the effect originates in the nickelate itself, not at the interface with another material.

The most striking discovery is that on the material's property map, this new superconducting "island" is separated from the known "mainland" by a wide region where superconductivity is entirely absent. Previously, it was thought that superconductivity in nickelates smoothly intensifies with increased doping, reaches a peak, and then declines, like a hill. Now it's clear that at low doping it appears, disappears, and then reappears at higher doping. The two regimes also differ in their response to magnetic fields: in the new regime, superconductivity depends much more strongly on the field direction. This points to a different intrinsic nature of the phenomenon.

This discovery overturns the view of nickelates. They can no longer be considered mere twins of cuprates: they have their own, as yet unsolved, physics of superconductivity. Pure nickelate conducts current without loss at temperatures still far from room temperature, but the very existence of two different mechanisms in one family of materials promises new paths to understanding high-temperature superconductivity. Perhaps the key lies not in doping, but in preserving the perfect order of the crystal.

Original abstract

as written by the authors arXiv:2607.16684

Infinite-layer nickelates have been widely viewed as cuprate analogs in which superconductivity emerges and forms a superconducting dome centered around 10-20% cation substitution. Here we show that pristine and stoichiometric PrNiO2, without cation substitution, exhibits intrinsic superconductivity characterized by zero resistance and diamagnetism in uncapped films. Through heterostructure engineering, we further exclude an interfacial origin of the superconductivity. Remarkably, zero-resistance superconductivity is consistently observed in trivalent-substituted PrNiO2, whereas it is rapidly suppressed by dilute divalent substitution. Combined with angle-resolved photoemission studies, these results indicate that such a new superconducting regime is confined to within 3% additional hole doping from pristine PrNiO2. Furthermore, this phase is separated from the previously established superconducting dome around ~ 20% divalent doping by a non-superconducting region in the phase diagram, and is further distinguished by a remarkably stronger upper-critical-field anisotropy. These findings establish a unique separated superconducting regime, suggesting that infinite-layer nickelates are not merely cuprate analogs but host distinct superconducting physics.