Superconducting Quintuple-Layer Square-Planar Nickelates—Superconducting and Electronic Properties (Part I)

Since the discovery of high-temperature superconductivity in the copper oxide materials, there have been sustained efforts to both understand the origins of this phase and discover new cuprate-like superconductors. One prime materials candidate has been the rare-earth nickelates and indeed superconductivity was recently discovered in the doped compound Nd_0.8Sr_0.2NiO₂. Undoped NdNiO₂ belongs to a series of layered square-planar nickelates with chemical formula Nd_n+1Ni_nO_2n+2 and is known as the ‘infinite-layer’ (n = ∞) nickelate. Here, we present the superconducting and electronic properties of molecular beam epitaxy-synthesized Nd₆Ni₅O₁₂, the quintuple-layer (n = 5) member of this series, which achieves optimal cuprate-like electron filling (3<i>d</i>^8.8) without chemical doping. We observe a superconducting transition beginning at ~13 K. [1] Electronic structure calculations, in tandem with magnetoresistive and spectroscopic measurements, suggest that Nd₆Ni₅O₁₂ interpolates between cuprate-like and infinite-layer nickelate-like behavior. By engineering a distinct superconducting nickelate, we identify the square-planar nickelates as a new family of superconductors which can be tuned via both doping and dimensionality. In part II of this talk, we further expound on the synthetic strategies of the layered nickelates including Nd₆Ni₅O₁₂.<br/>[1] GA Pan et al. Superconductivity in a quintuple-layer square-planar nickelate. arXiv:2109.09726.<br/>[2] D Ferenc Segedin et al. Superconducting Quintuple-layer Square-planar Nickelates: Synthetic Strategies and Challenges (Part II). MRS Bulletin Spring 2022.