Magnetic excitations in strained infinite-layer nickelate PrNiO₂ films

Strongly correlated materials respond sensitively to external perturbations such as strain, pressure, and doping. In the recently discovered superconducting infinite-layer nickelates, the superconducting transition temperature can be enhanced via only ~ 1% compressive strain-tuning with the root of such enhancement still being elusive. Using resonant inelastic x-ray scattering (RIXS), we investigate the magnetic excitations in infinite-layer PrNiO₂ thin films grown on two different substrates, namely SrTiO₃ (STO) and (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 (LSAT) enforcing different strain on the nickelates films. The magnon bandwidth of PrNiO₂ shows only marginal response to strain-tuning, in sharp contrast to the enhancement of the superconducting transition temperature T_c in the doped superconducting samples. These results suggest the bandwidth of spin excitations of the parent compounds is similar under strain while T_c in the doped ones is not, and thus provide important empirics for the understanding of superconductivity in infinite-layer nickelates.