Vortex penetration and flux relaxation with arbitrary initial conditions in non-ideal and ideal superconductors

TL;DR

This paper generalizes models of vortex penetration and flux relaxation in superconductors to arbitrary initial conditions, enabling better predictions of internal fields and critical currents in both ideal and non-ideal materials.

Contribution

It introduces a method to convert processes with arbitrary initial conditions into standard forms, expanding the applicability of existing models for superconductor vortex dynamics.

Findings

Conversion of non-zero initial internal field processes to zero initial field processes.

Prediction of melting internal field from flux relaxation starting with lower internal fields.

Vortex penetration is time-dependent in ideal superconductors due to surface barriers.

Abstract

Vortex penetration and flux relaxation phenomenon carry the information about the pinning ability, and consequently current-carrying ability, of a type-II superconductor. However, the theoretical descriptions to these phenomena are currently limited to the cases with special initial conditions. A generalization to the recently developed infinite series models is presented here. It is shown that one can convert a vortex penetration process with a non-zero initial internal field into a process with a zero initial internal field by introducing some time parameters. Similarly, one can also convert a flux relaxation process starting with an arbitrary internal field into a process starting with a melting internal field by introducing a virtual time interval. Therefore, one can predict the melting internal field (or critical current density) from a flux relaxation process starting with a lower internal field. Finally, it is shown that the vortex penetration process in an ideal superconductor is strongly time dependent because of the surface barrier and internal field repulsive force. But the flux relaxation process does not occur in the ideal superconductor.