Tuning the Lower Limit to the Vortex Creep Rate

In superconductors, the critical current density, Jc, depends on the dynamics of vortices, penetrated magnetic flux lines whose motion introduces energy loss. This motion can be induced by current-induced forces and thermal energy (creep). Thankfully, material defects can slow down vortex motion, resulting in a dramatic improvement in Jc. In a recent study, it was found that the ultimate theoretical lower limit to the vortex creep rate depends on the Ginzburg number, Gi, which in turn depends on material-specific parameters such as the coherence length, penetration depth, and critical temperature. The typical approach to minimizing creep is to modify the defect landscape to reach our proposed lower limit. In this study, we aim to reduce the theoretical lower limit itself by tuning the Ginzburg parameter in iron-based superconductors through doping and subsequently test whether we do indeed observe slower vortex creep. If successful, this approach could lead to extremely slow creep rates in materials and therefore unprecedentedly high current carrying capacities.