Doping and pressure effects on Superconductivity and crystal structures of La_3-xR_xNi₂O_7-δ

The recent discovery of superconductivity in pressurized La₃Ni₂O₇ has attracted significant attention due to its high critical temperature and structural similarities to cuprate superconductors. This study explores the role of the lanthanum site by partially substituting La with different rare earth elements (R). Systematic measurements were performed to explore the doping and pressure effects on crystal structure, magnetism, and electrical transport properties of La_3-xR_xNi₂O_7-δ. Our results as well as other reports showed that low levels of R -doping enhance lattice crystallinity, and favor phase formation, while higher R content leads to significant lattice distortions and the emergence of new crystal structures. High-pressure electrical resistivity measurements reveal dome-shaped superconductivity, with anomalies in the resistance versus pressure phase diagram likely associated with pressure-induced structural transitions. These findings broadens the potential scope of superconducting Ruddlesden-Popper nickelates and provide new insights into the roles of crystal structure in the emergent superconductivity.