Infrared studies ofab-plane oriented oxide superconductors

Abstract

New results covering a wide frequency and temperature range are presented for the infrared properties of $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ for light polarized in the $\mathrm{ab}$ plane. The normal-state optical conductivity can be described by two processes: a low-frequency Drude absorption that tracks the temperature dependence of the dc conductivity and a temperature-independent midinfrared band. In the superconducting state most of the oscillator strength of the Drude absorption moves to zero frequency and the reflectance spectrum is dominated by a plasma edge at 500 ${\mathrm{cm}}^{-1\mathrm{}}$. A superconducting gap cannot be seen in our spectra.