KONDO COUPLING INDUCED CHARGE GAP IN CE3BI4PT3

Measurements of the infrared reflectivity of the Kondo insulator Ce3Bi4Pt3 as reported. Near room temperature the charge dynamics are comparable to those of a heavy fermion compound in the incoherent regime; however, below 100 K the depletion of the low frequency conductivity signifies the development of a charge gap at low frequency (approximately 300 cm-1). The temperature dependence of the depleted spectral weight scales with the quenching of the Ce 4f moments, demonstrating that the gap formation is due to the local Kondo coupling of charge carriers to the Ce magnetic moments. The spectral weight which disappears as the gap forms must be displaced to energies much larger than the gap.