How high can $T_{c}$ reach in ambient-pressure nickelate films
In plain words
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 statement
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.
What would settle it
Films with zero resistance and diamagnetic shielding at the predicted ceiling, together with structural refinement showing the strain state.
Status in the literature
Unverified 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).