Abstract
We have measured both the transmittance (scrT) and reflectance (scrR) for several thin films over the frequency range from 20 to 360 at temperatures between 20 and 300 K. The films, grown on MgO substrates by pulsed laser ablation, are highly a-b-plane oriented. We use scrT and scrR to extract the optical conductivity, and find good agreement with results from Kramers-Kronig analysis of reflectance measurements alone. The transmittance is consistent with a two-component dielectric function consisting of Drude (free-carrier) and midinfrared (bound-carrier) absorption. The Drude relaxation rate varies linearly with temperature, and compares well with values obtained from the measured dc resistivity. We use a two-fluid model for the superconducting state and obtain a BCS-like temperature dependence for the superfluid density. A superconducting gap is not observed in our spectra.
- Received 3 August 1990
DOI:https://doi.org/10.1103/PhysRevB.43.10383
©1991 American Physical Society