Superconductivity of Y₂C₃ investigated by specific heat measurement

We report newly synthesized high-purity samples of Y₂C ₃ with various T_c's (11.6, 13.9, and 15.2 K) and compared their superconducting properties by magnetization and specific heat measurements. From specific heat measurements, the fitting below T_c to the electron specific heat of each sample has an exp(-1/T) dependence, as predicted by BCS theory, rather than a Tⁿ dependence, as for superconductors with an anisotropic symmetry of superconductivity. These results indicate that the symmetry of the superconductivity of Y₂C ₃ is that of an isotropic s-wave. From the fitting below T _c, we estimated 2Δ/k_BT_c to be 3.6, 3.9, and 4.1 for the 11, 13, and 15 K samples, respectively. We found that T _c of Y₂C₃ was correlated to the Sommerfeld coefficient, and that the high-T_c material was in a stronger coupling regime than the low-T_c material.