Flux transport in nanostructured high-Tc films at microwave frequencies

The understanding of flux transport in micro- and nanostructured superconducting systems that are exposed to an electromagnetic field at microwave frequencies is of interest for basic aspects of vortex matter and for potential application of superconductivity in fluxonic devices. We report on the combination of dc and microwave electronic measurements on submicron-patterned high-Tc films. The frequency dependence of the forward transmission coefficient S21 indicates that the mechanism of flux transport depends on the velocity of vortices. At low frequencies, flux transport via Abrikosov vortices is present leading to additional microwave losses. Above a geometrically defined frequency, a different, loss-free mechanism seems to be responsible for flux transport. This mechanism most likely represents a phase-slip type of mechanism. The limiting vortex velocity obtained from the frequencies dependence of the microwave properties agrees with the Larkin-Ovchinnikov critical vortex velocity determined via dc pulse measurements. In spite of the change of mechanism, guidance of flux persists in these nano-patterns up to high frequencies.