Superconductivity in PrNiO₂ Infinite‐Layer Nickelates

Abstract Several reports about infinite‐layer nickelate thin films suggest that the superconducting critical temperature versus chemical doping phase diagram has a dome‐like shape, similar to cuprates. Here, a highly reproducible superconducting state in undoped PrNiO₂ thin films grown on SrTiO₃ are demonstrated. Scanning transmission electron microscopy measurements show coherent infinite‐layer phase with no visible stacking‐fault defects, an overall high structural quality where possible unintentional chemical doping or interstitial oxygen, if present, sum well below the measurable threshold of the technique. X‐ray absorption measurements show very sharp features at the Ni L_3,2‐edges with a large linear dichroism, indicating the preferential hole occupation of Ni¹⁺‐3 orbitals in a square planar geometry. Resonant inelastic X‐ray scattering measurements reveal sharp magnon excitations of 200 meV energy at the magnetic Brillouin zone boundary, highly resonant at the Ni^{1 +} absorption peak. The results indicate that, when properly stabilized, infinite‐layer nickelate thin films are superconducting without chemical doping.