We have measured the room-temperature reflectivity of 90-K single crystals YBa2Cu3O7 in the frequency range 6009000 cm-1. The reflectivity R in these highly conducting samples (ab=150 cm at 290 K) is found to be higher than in previous reports. We fit R to a simple Drude-Lorentz model and compare the fit parameters with the dc transport values. (The effective-mass ratio of the carriers is found to be 2.0, and the scattering rate Latin small letter h with stroke/ is 3.1kBT at room temperature.) Ellipsometry measurements have also been performed using transverse-electric and transverse-magnetic polarizations. The dielectric dispersion derived from ellipsometry shows some important deviations from the Drude-Lorentz model. Reflectivity data from nonsuperconducting crystals of Bi2Sr2CuO6+y are also reported.
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