Dielectric waveguide with a YBa₂Cu₃O_6+x boundary layer at 94 GHz

We report on the measurement of the millimeter wave transmission properties of a dielectric waveguide with a YBa₂Cu₃O_6+x boundary layer. The transmitted power and phase shift of a 94 GHz signal propagating through the dielectric waveguide structure was measured over the temperature range of 77-150 K. The transmitted power was observed to depend upon temperature due to the dissipation of the millimeter wave signal in the YBa₂Cu₃O_6+x boundary layer. Thereby the temperature dependence of the normal-state ac conductivity was measured. The experimental data were fitted to a Drude model for the normal-state ac conductivity of the YBa₂Cu₃O_6+x. The temperature dependence of the Drude scattering time was obtained. The scattering time was found to decrease with decreasing temperature and was 7.5-11.2 ps in magnitude.