Optical evidence for mass enhancement of quasiparticles in pyrochlore Cd${}_2$Re${}_2$O${}_7$

Abstract

We report on the results of optical studies of the newly discovered superconductor Cd${}_2$Re${}_2$O${}_7$ 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 mid-infrared excitation band. Detailed analysis reveals a moderate enhancement of the effective mass at low temperature and low frequency.

5 pages, 4 figures. to be published in Phys. Rev. B, scheduled issue: 01 August 2002