Superconductivity and Magnetic Fluctuations inCd2Re2O7via Cd Nuclear Magnetic Resonance and Re Nuclear Quadrupole Resonance

We report Cd nuclear magnetic resonance (NMR) and Re nuclear quadrupole resonance (NQR) studies on $\mathrm{Cd}{}_2{\mathrm{Re}}_2{\mathrm{O}}_7$, the first superconductor among pyrochlore oxides $\left(T_c\simeq 1\mathrm{K}\right)$. The Re NQR spectrum at zero magnetic field below 100 K rules out any magnetic or charge order. The spin-lattice relaxation rate below $T_c$ exhibits a pronounced coherence peak and follows the weak-coupling BCS theory with nearly isotropic energy gap. The results of Cd NMR point to a moderate ferromagnetic enhancement at high temperatures followed by a rapid decrease of the density of states below the structural transition temperature of 200 K.