The propagation characteristics of wave-guiding structures with very thin superconductors; application to coplanar waveguide YBa2Cu3O7-x resonators

The authors have analyzed the propagation characteristics of wave-guiding structures with superconductors which are thin compared to the magnetic penetration depth. The complex propagation constant is evaluated within the framework of the modified spectral domain method without the need for numerical calculations in the complex plane. Good agreement is found with the results of other methods. The numerical analysis is instrumental in deducing results for the penetration depth and the surface resistance of YBa2Cu3O7-x thin films on sapphire with a PrBa2Cu3O7-x buffer layer. They confirm recent observations of a non-single-gap BCS temperature dependence