Superconductivity in a quintuple-layer square-planar nickelate

This webinar will focus on the experimental design and synthesis of new quantum materials at the atomic scale. Our tool of choice is reactive oxide molecular beam epitaxy (MBE).

MBE enables atomic-layer-by-atomic-layer control over inorganic materials synthesis. In tandem with characterization techniques, including electronic transport, synchrotron spectroscopies, and importantly, X-ray diffraction enabled by the Malvern Panalytical diffractometer, we used MBE to create a new, layered nickel oxide-based superconductor.

Since the discovery of high-temperature superconductivity in copper oxide materials, there have been sustained efforts both to understand the origins of this phase and to discover new ‘cuprate-like’ superconducting materials. One prime materials candidate was the rare-earth nickelates and, indeed, superconductivity was recently discovered in the doped compound Nd0.8Sr0.2NiO2.

Undoped NdNiO2 belongs to a series of layered square-planar nickelates with the chemical formula Ndn+1NinO2n+2, and is known as the ‘infinite-layer’ (n = ∞) nickelate. Using reactive oxide MBE, we designed and synthesized the quintuple-layer (n = 5) member of this series, Nd6Ni5O12.

This layered compound is a unique lower-dimensional version of NdNiO2, as it comprises NdO2 spacer layers that sandwich every five layers of NdNiO2. Importantly, Nd6Ni5O12 achieves optimal cuprate-like electron filling (3d8.8) without chemical doping. We observe a superconducting transition beginning at ~13 K.

Electronic structure calculations, in tandem with magnetoresistive and spectroscopic measurements, suggest that Nd6Ni5O12interpolates between cuprate-like and infinite-layer nickelate-like behavior. In engineering this distinct superconducting nickelate, we have identified the square-planar nickelates as a new family of superconductors, which can be tuned via both doping and dimensionality.