Phonon density of states of the infinite layer nickelate Nd_0.8Sr_0.2NiO₂

One of the main mysteries of high-temperature superconductivity in oxides is why this has so far only been observed for cuprates, but not for other oxides with transition metals exhibiting similar electronic properties. The recent report of superconductivity up to 15K in a thin film nickelate with similar crystal and electronic structures to that of the cuprates, suggests that these infinite-layer nickelates could harbor superconductivity with the same underlying pairing mechanism as the cuprates. Here we report inelastic neutron scattering measurements performed on a bulk sample of Nd_0.8Sr_0.2NiO₂, the same nominal composition for which superconductivity was observed in thin film form grown on a SrTiO₃ substrate. We will discuss the implications of our results, in particular the measured phonon density of states, on possible superconducting mechanisms in this compound.