Recent progress in nickelate superconductors

The discovery of superconductivity in nickelate compounds has opened new avenues in the study of high-temperature superconductors. Here we provide a comprehensive overview of recent progress in the field, including all different nickelate systems, reduced-Ruddlesden-Popper-type infinite layer LaNiO2, Ruddlesden-Popper-type bilayer La3Ni2O7 and trilayer La4Ni3O10. We begin by introducing the superconducting properties of the hole-doped LaNiO2 system, which marked the starting point for nickelate superconductivity. We then turn to the bilayer La3Ni2O7 system, discussing both its high-pressure and thin-film superconducting phases. This is followed by an examination of the trilayer La4Ni3O10 system and other related multilayer nickelates. Throughout the review, we highlight emerging trends, key challenges, and open questions. We conclude by addressing current limitations in materials synthesis and characterization, and future directions that may help uncover the mechanisms driving superconductivity in these complex oxide systems.