Superconductivity onset above 60 K in ambient-pressure nickelate films

Abstract

ABSTRACT Ambient-pressure superconductivity in nickelates has been capped at an onset transition temperature (Tconset) of ∼50 K, a value that remains lower than those of the cuprate (∼133 K) and iron-based (∼55 K) counterparts, despite the promise shown under high pressure. Here, we report ambient-pressure superconductivity onset at ∼63 K in epitaxial (La,Pr)3Ni2O7 thin films grown under compressive strain on SrLaAlO4 substrates. This Tc leap is enabled by pushing our gigantic-oxidative atomic-layer-by-layer epitaxy (GAE) method into an extreme non-equilibrium growth regime. It simultaneously enhances kinetics via higher temperatures and achieves full oxygenation in situ without post-annealing. Synchrotron X-ray diffraction and scanning transmission electron microscopy confirm that this approach yields films of large-scale crystalline purity, overcoming the inherent metastability of the strained superconducting phase. Transport measurements reveal a zero-resistance temperature (Tczero) reaching ∼37 K, while mutual inductance measurements demonstrate a robust diamagnetic transition starting at ∼23 K. These films exhibit a systematic evolution in their normal-state resistivity–temperature curve: the power-law exponent α evolves from Fermi-liquid-like (α ∼ 2) at lower Tconset to strange-metal-like (α ∼ 1) in higher Tconset samples, directly linking the enhanced superconductivity to non-Fermi liquid behavior. Mapping the vortex melting phase diagram by the mutual inductance technique further reveals the 2D melting limit suppressed to near zero, which demonstrates significantly stronger interlayer coupling than that of cuprates. These results identify the nickelates as ambient-pressure strange-metal high-temperature superconductors with strong interlayer coupling.