  After the reward of more than two decades of pursuit on the high-Tc cuprate
analog with the hope to obtain a better understanding of the mechanism of
high-Tc superconductivity, the discovery of superconductivity in the
infinite-layer nickelate brings more mystery to the picture than expected. Tops
in the list of questions are perhaps (1) absence of superconductivity in the
bulk nickelate and limited thickness of the infinite-layer phase in thin film,
(2) absence of superconductivity in the La-nickelate despite it being the
earliest studied rare-earth nickelate, and the role of 4f orbital in the recipe
of superconductivity, (3) absence of Meissner effect and suspect of the origin
of superconductivity from the interface, (4) whether nickelate hosts similar
pairing symmetry to the single-band high-Tc cuprates or multiband iron-based
superconductor. In this perspective article, we will discuss the following
aspects: (1) stabilization of the infinite-layer phase on the SrTiO3(001)
substrate and the thickness dependency of observables; (2) rare earth
dependence of the superconducting dome and phase diagram on the (La/Pr/Nd)-
infinite-layer nickelate thin film; (3) experimental aspects of the measurement
of Meissner effect; (4) theoretical framework and experimental study of the
pairing symmetry of infinite-layer nickelate superconductor.
