Theory of fractional vortex escape in a 0-kappa long Josephson junction

TL;DR

This paper models the escape dynamics of fractional vortices in long Josephson junctions, revealing how topological charge influences escape rates under thermal and quantum fluctuations.

Contribution

It introduces a mapping of Josephson phase dynamics to a particle in a metastable potential, predicting escape rates based on vortex topological charge.

Findings

Escape rate depends on vortex topological charge.

Thermal and quantum fluctuations enable escape at subcritical currents.

Derived effective potential parameters for fractional vortices.

Abstract

We consider a fractional Josephson vortex in an infinitely long 0-kappa Josephson junction. A uniform bias current applied to the junction exerts a Lorentz force acting on a vortex. When the bias current becomes equal to the critical (or depinning) current, the Lorentz force tears away an integer fluxon and the junction switches to the resistive state. In the presence of thermal and quantum fluctuations this escape process takes place with finite probability already at subcritical values of the bias current. We analyze the escape of a fractional vortex by mapping the Josephson phase dynamics to the dynamics of a single particle in a metastable potential and derive the effective parameters of this potential. This allows us to predict the behavior of the escape rate as a function of the topological charge of the vortex.