  Strongly correlated materials often respond sensitively to the external
perturbations. In the recently discovered superconducting infinite-layer
nickelates, the superconducting transition temperature can be dramatically
enhanced via only ~1% compressive strain-tuning enabled by substrate design.
However, the root of such enhancement remains elusive. While the
superconducting pairing mechanism is still not settled, magnetic Cooper pairing
- similar to the cuprates has been proposed. Using resonant inelastic x-ray
scattering, we investigate the magnetic excitations in infinite-layer PrNiO2
thin films for different strain conditions. The magnon bandwidth of PrNiO2
shows only marginal response to strain-tuning, in sharp contrast to the
striking enhancement of the superconducting transition temperature Tc in the
doped superconducting samples. These results suggest the enhancement of Tc is
not mediated by spin excitations and thus provide important empirics for the
understanding of superconductivity in infinite-layer nickelates.
