Optical evidence for mass enhancement of quasiparticles in pyrochlore Cd2Re2O7 -: art. no. 014534

We report on the results of optical studies of the superconductor Cd2Re2O7 in the normal state. We show that the compound has an exotic metallic state at low temperature. The optical conductivity spectrum exhibits two distinct features: a sharp renormalized resonance mode at zero frequency and a broad midinfrared excitation band. Detailed analysis reveals a moderate enhancement of the effective mass at low temperature and low frequency.