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Abstract |
We have measured the room-temperature reflectivity of "90-K" single crystals YBa_2Cu_3O_7 in the frequency range 600-9000 cm^−1. The reflectivity R in these highly conducting samples (ρ_ab=150 μΩ cm a...t 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 ħ/τ is 3.1k_B T 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 Bi_2Sr_2CuO_<6+y> are also reported.show more
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