The nickelate bridge between cuprate and iron-based superconductivity

Abstract The nickelates present two distinct subfamilies: the square-planar nickelates, which are structural and electronic analogs to the single-orbital, strongly correlated cuprates; and the Ruddlesden-Popper nickelates, which exhibit a multi-orbital character reminiscent of the iron-based superconductors. This duality uniquely positions the nickelate family as a bridge between the two canonical systems, offering an unprecedented opportunity to comparatively study the physics of both within a single material platform. While the thermodynamic metastability of their superconducting phases presents significant synthesis challenges, shifting the focus to atomic-scale engineering of thin films, the nickelates provide a versatile new laboratory for deciphering the puzzle of unconventional superconductivity and exploring pathways to higher transition temperatures.