TIME-DOMAIN MEASUREMENT OF THE SURFACE-RESISTANCE OF YBA2CU3O7 SUPERCONDUCTING FILMS UP TO 500 GHZ

We measure the surface resistance and surface reactance of high quality YBa2Cu3O7 superconducting films from 10 GHz to 500 GHz using time-domain propagation measurements of picosecond electrical pulses on coplanar transmission lines. For the surface resistance, we find a square law dependence with frequency almost up to 500 GHz and a crossover of the losses of gold and YBa2Cu3O7 films at 77 K at roughly 100 GHz. We successfully model the pulse propagation using the Mattis-Bardeen theory for the frequency dependent conductivity of YBa2Cu3O7. Good quantitative agreement of the surface resistance and surface reactance with this theory is obtained. Finally, we theoretically study the potential of YBa2Cu3O7 superconducting films and equivalent gold and superconducting films for high-speed applications.