Superconductivity in the correlated pyrochloreCd2Re2O7

We report the observation of superconductivity in high-quality ${\mathrm{Cd}}_2{\mathrm{Re}}_2{\mathrm{O}}_7$ single crystals with room-temperature pyrochlore structure. Resistivity and ac susceptibility measurements establish an onset transition temperature $T_c^{\mathrm{onset}}=1.47\mathrm{}\hspace{0.5em}\mathrm{K}$ with transition width $\Delta T_c=0.25\mathrm{}\hspace{0.5em}\mathrm{K}.$ In applied magnetic field, the resistive transition shows a type-II character, with an approximately linear temperature-dependence of the upper critical field $H_{c2\mathrm{}}.$ The bulk nature of the superconductivity is confirmed by the specific heat jump with $\Delta C=37.9\mathrm{}\hspace{0.5em}\mathrm{mJ}/\mathrm{m}\mathrm{o}\mathrm{l}-\mathrm{K}.$ Using the γ value extracted from normal-state specific heat data, we obtain $\Delta C/\gamma T_c=1.29,$ close to the weak coupling BCS value. In the normal state, a negative Hall coefficient below 100 K suggests electronlike conduction in this material. The resistivity exhibits a quadratic T dependence between 2 and 60 K, i.e., $\rho ={\rho }_0{+AT}^2,$ indicative of Fermi-liquid behavior. The values of the Kadowaki-Woods ratio $\mathrm{A}/{\gamma }^2$ and the Wilson ratio are comparable to that for strongly correlated materials.