Mark W. Coffey

Radio-frequency surface impedance of type-II superconductors: Dependence upon the magnitude and angle of an applied static magnetic field

The application of a static magnetic field introduces vortices into a type-II superconductor. The dynamic response of these vortices strongly affects the surface impedance (surface resistance and surface reactance) of the superconductor. Using a self-consistent approach for including the influence of the vortices upon the complex-valued radio-frequency penetration depth, we calculate in this paper how the surface impedance depends upon the static magnetic fields magnitude and angle relative to the surface and to the rf magnetic field. The surface resistance is maximized when the induced rf currents are perpendicular to the static field.