Multivortex and giant vortex states near the expulsion and penetration fields in thin mesoscopic superconducting squares

摘要

The temperature dependence of the vortex penetration and expulsion magnetic fields are investigated, both theoretically and experimentally, for mesoscopic superconducting squares. The small-tunnel-junction method is used to determine the transition fields between the different vortex states. We found that the penetration fields decrease with increasing temperature, while the expulsion fields for a particular vorticity may increase, decrease or be independent of temperature. Using the Ginzburg-Landau theory we link the different temperature dependencies to the configuration of the vortex state, i.e. giant vortex state versus multivortex state. The vortex state consisting of four vortices has a larger stability region which is most pronounced in a certain high-temperature range.