Far-infrared c-axis conductivity of flux-grown Y1-xPrxBa2Cu3O7 single crystals studied by spectral ellipsometry

The far-infrared c-axis conductivity of flux-grown Y1-xPrxBa2Cu3O7 single c rystals with 0.2 less than or equal to x less than or equal to 0.5 has been studied by spectral ellipsometry. We find that the e-axis response exhibit s spectral features similar to deoxygenated underdoped YBa2Cu3O7-delta, i.e ., a pseudogap develops in the normal state, the phonon mode at 320 cm(-1) exhibits an anomalous T dependence, and an additional absorption peak forms at low temperature. This suggests that the T-c suppression in flux grown P r-substituted crystals is caused by a decrease of the hole content and/or b y carrier localization rather than by pair breaking.