Superconductivity in Ruddlesden-Popper nickel oxides

In 2023, superconductivity was, for the first time, observed in bulk Ruddlesden-Popper nickelates, in a compressed lanthanum-bearing nickel oxide. Different La-containing nickelate stoichiometries were soon after shown to also superconduct, followed by multiple reports of superconductivity in Pr₄Ni₃O₁₀ under static pressure. However, this critical phenomenon remains to be explored in nickel alloys grown with elements further down the lanthanide series. The decrease of ionic radius as a function of increasing Z in lanthanides presents another way of tuning the lattice, which could correlate with the pressure threshold needed to drive Ruddlesden-Popper nickelates into a bulk superconducting state.