Anomalous Dome-like Superconductivity in RE₂(Cu_1-xNi_x)₅As₃O₂ (RE = La, Pr, Nd)

A significant manifestation of interplay of superconductivity and charge density wave, spin density wave, or magnetism is a dome-like superconducting critical temperature (T_c) in cuprate, iron-based, and heavy Fermion superconductors. Pesudogap, quantum critical point, and strange metals emerge in different doping ranges. Exploring dome-like T_c in new superconductors is of interest to detect emergent effects. Here we report the superconductivity in a new layered Cu-based compound RE₂Cu₅As₃O₂ (RE = La, Pr, Nd), in which the T_c exhibits dome-like variation with a maximum T_c of 2.5, 1.2, and 1.0 K with substitution of Cu by large amount of Ni ions. Simultaneously, the structural parameters like As-As bond length and c/a ratio exhibit unusual variations as the Ni-doping level goes through the optimal value. The robustness of superconductivity, up to 60% of Ni doping, reveals the unexpected impurity effect on inducing and enhancing superconductivity in these novel layered materials.