Energy Dependent Scattering in Heavy Fermion Compounds

The Heavy Fermion compounds (HFC) exhibit effective masses enhanced by orders of magnitude over calculated band masses. Using far-infrared (FIR) spectroscopy as a probe of the conductivity, and hence the scattering in HFCs, we observe the frequency dependent mass enhancement as arising from interactions which also lead to a dramatic increase and eventual saturation of the fermion scattering at frequencies higher than a characteristic energy analogous to T sub K in Kondo systems.