Vortex Dynamics at the transition to the normal state in YBCO films

TL;DR

This paper models vortex dynamics in YBCO films near the transition to the normal state, explaining current-voltage behavior and vortex depinning effects through thermally activated vortex motion along twin boundaries.

Contribution

It introduces a new description of vortex behavior in YBCO films, linking vortex depinning and thermal activation to observed electrical discontinuities at the transition.

Findings

Discontinuity in current-voltage curves explained by vortex depinning.

Vortex activation energy approaches zero near critical temperature.

Model predictions align with experimental data.

Abstract

We propose a description of the vortex dynamics in YBCO films from the critical to the normal states. This description supposes that the vortex motion is thermally activated along the twin boundaries of the films. The discontinuity observed in the current-voltage curves at the transition to the normal state is explained by the sudden increase in the dissipated power rate due to vortex depinning. However, near the critical temperature, this phenomenon does not occur because the vortex activation energy is near zero. We also show how the current at the transition to the normal state can be computed from the current-voltage curves measured at low currents. The predictions of this description are compared to the data published by Gonzalez et al. [Phys.Rev.B68,054514 (2003)].