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Title: How high can $T_{c}$ reach in ambient-pressure nickelate films
Plain: Squeezing bilayer nickelate films by growing them on a substrate with smaller atomic spacing mimics high pressure; the question is whether this can reach the 80 K seen under pressure.
Precise: Determine the highest $T_c$ attainable in bilayer nickelate films at ambient pressure through epitaxial compressive strain, rare-earth substitution and oxygenation, and whether it can match the $\sim 80 \text{ to } 96\,\mathrm{K}$ reached under hydrostatic pressure. An answer is a measured zero-resistance $T_c$ with Meissner response, or a model of $T_c$ versus in-plane lattice constant and c-axis structure that predicts the ceiling.
Settled by: Films with zero resistance and diamagnetic shielding at the predicted ceiling, together with structural refinement showing the strain state.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: Onset $T_{c}$ rose from about $40\ \mathrm{K}$ (early 2025) to about $63\ \mathrm{K}$, with zero resistance near $37\ \mathrm{K}$, in (La,Pr)3Ni2O7 films on SrLaAlO4 (reported late 2025, published 2026).
Posed since: 2025