Nodeless superconducting gap in the caged-type superconductors Y₅Rh₆Sn₁₈and Lu₅Rh₆Sn₁₈

Abstract

Low-temperature thermal conductivity measurements were performed on the single crystal of caged-type superconductors Y 5 Rh 6 Sn 18 and Lu 5 Rh 6 Sn 18 down to 80 mK. In zero magnetic field, no residual linear term κ 0 / T is found for either superconductor. At low field, the κ 0 / T of these two superconductors shows weak field dependence. These results exclude the nodal superconducting gap in Y 5 Rh 6 Sn 18 as revealed by recent specific heat measurements, and suggest that the caged-type superconductors R 5 Rh 6 Sn 18 (R = Y and Lu) may have a common nodeless superconducting gap.