Size effects in the nonlinear resistance and flux creep in a virtual Berezinskii-Kosterlitz-Thouless state of superconducting films

TL;DR

This paper investigates how the size of superconducting films influences their nonlinear electrical resistance and vortex dynamics, revealing that geometry can significantly alter flux creep and BKT-like behavior.

Contribution

It introduces a theoretical model accounting for size effects on vortex interactions and flux creep, predicting geometry-dependent electric field-current relations in superconducting films.

Findings

Size effects significantly alter the $E-I$ relation in superconducting films.

Virtual vortex-antivortex unbinding can dominate transport behavior.

Film geometry can tune the electric response and resistance.

Abstract

We show that the size effects radically affect the electric field-current ($E-I$) relation of superconducting films. We calculate $E(J)$ due to thermally-activated hopping of single vortices driven by current $I$ across the film in a magnetic field $H$, taking into account interaction of free vortices with their antivortex images and peaks in the Meissner currents at the film edges. Unbinding of virtual vortex-antivortex pairs not only mimics the transport uniform BKT behavior, it can dominate the observed $E(J)$ and result in the field-dependent ohmic resistance at small $I$. We show that $E(I)$ can be tuned by changing the film geometry and propose experimental tests of this theory.