Thermal depinning and creep in strong pinning theory

TL;DR

This paper investigates the effects of thermal fluctuations on strong vortex pinning in type-II superconductors, revealing that pinning and creep effects persist beyond the critical drive and modify the force-velocity relationship.

Contribution

It challenges the common belief that pinning and creep vanish above the critical drive by showing they persist and influence the force-velocity characteristic in strong pinning theory.

Findings

Pinning and thermal creep extend beyond the critical drive.

Force-velocity curve retains its zero-temperature shape.

Thermal creep causes a downward shift of the critical drive.

Abstract

Pinning and thermal creep determine the response of numerous systems containing superstructures, e.g., vortices in type II superconductors, domain walls in ferroics, or dislocations in metals. The combination of drive and thermal fluctuations lead to the superstructure's depinning and its velocity $v$ determines the electric, magnetic, or mechanical response. It is commonly believed that pinning and creep collapse above the critical drive $F_c$, entailing a sharp rise in the velocity $v$. We challenge this perception by studying the effects of thermal fluctuations within the framework of strong vortex pinning in type-II superconductors. In fact, we show that pinning and thermal creep persist far beyond the critical force. The resulting force-velocity characteristic largely maintains its zero-temperature shape and thermal creep manifests itself by a downward renormalisation of the critical drive. Such characteristics is in agreement with Coulomb's law of dry friction and has been often observed in experiments.