Effect of physical and chemical pressure on the superconductivity of cage-type compound Lu5Rh6Sn18

Lu₅Rh₆Sn₁₈ is one of the cage-type superconductors with superconducting transition temperature Tc=4.12 K. Here we investigate the effect of pressure on the superconductivity in Lu₅Rh₆Sn₁₈ by combining high-pressure electrical transport, synchrotron x-ray diffraction (XRD), and chemical doping. Application of high pressure can enhance both the metallicity and the superconducting transition temperature in Lu₅Rh₆Sn₁₈. Tc is found to show a continuous increase reaching up to 5.50 K at 11.4 GPa. Our high-pressure synchrotron XRD measurements demonstrate the stability of the pristine crystal structure up to 12.0 GPa. In contrast, Tc is suppressed after the substitution of La ions in Lu sites, inducing negative chemical pressure. Our study provides valuable insights into the improvement of superconductivity in caged compounds.