Current and Magnetic Field Dependences of a Superconducting Coplanar Waveguide Resonator

We fabricated superconducting coplanar waveguide resonator with leads for dc bias, which enables the ac conductivity measurement under dc bias. The current and the magnetic field dependences of resonance properties were measured, and hysteretic behavior was observed as a function of the dc driving current. The observed shift in the inverse of the quality factor and the center frequency were understood by considering both the motion of vortices and the suppression of the order parameter with dc current. Our investigation revealed that the strongly pinned vortices have little infuluence on the change in the center frequency, while it still affects that of the quality factor. Our results indicate that an accurate understanding of the dynamics of driven vortices is indispensable when we attempt to control the resonance properties with high precision.