Microwave surface impedance at 10 GHz and quasiparticle scattering in YBa2Cu3O7 films

Abstract
The surface impedance of superconducting YBa2Cu3O7 films as a function of temperature at 10 GHz has been measured in a parallel plate resonator geometry. The penetration depth λ(T), complex microwave conductivity σ(T), and quasiparticle scattering rate 1/τ(T) were also determined. After a rapid fall as T is lowered below Tc, the surface resistance Rs exhibits a linear dependence from 65 K down to 6 K. As T drops below Tc, the real part of the conductivity σ1 has a rapid rise, which is attributed to the observed dramatic increase in τ. The normal‐fluid density shows a linear behavior at low temperatures, which is inconsistent with s‐wave BCS superconductivity.