Effects of pressure and doping on Ruddlesden-Popper phases Lan+1NinO3n+1

Recently, the discovery of superconductivity with a critical temperature T c up to 80 K in Ruddlesden–Popper phases La n +1 Ni n O 3 n +1 ( n = 2) under pressure has garnered considerable attention. Up to now, the superconductivity was only observed in La 3 Ni 2 O 7 single crystal grown with the optical-image floating zone furnace under oxygen pressure. It remains to be understood the effect of chemical doping on superconducting La 3 Ni 2 O 7 as well as other Ruddlesden–Popper phases. Here, we systematically investigate the effect of external pressure and chemical doping on polycrystalline Ruddlesden–Popper phases. Our results demonstrate that the application of pressure and doping effectively tunes the transport properties of Ruddlesden–Popper phases. We find pressure-induced superconductivity up to 86 K in La 3 Ni 2 O 7 polycrystalline sample, while no signatures of superconductivity are observed in La 2 NiO 4 and La 4 Ni 3 O 10 polycrystalline samples under high pressure up to 50 GPa. Our study sheds light on the exploration of high- T c superconductivity in nickelates.