Vortex dynamics in disordered Josephson junction arrays: from plastic flow to flux flow

TL;DR

This paper investigates vortex dynamics in disordered Josephson junction arrays under external current, revealing a transition from plastic vortex flow with pinning and channel flow to a homogeneous flux flow at higher currents, characterized by a phase transition.

Contribution

It provides new insights into the dynamical phase transition between plastic flow and flux flow regimes in disordered Josephson junction arrays.

Findings

Plastic vortex flow with pinned vortices and channel flow at currents above critical.

Growth of flow channels with increasing bias current.

Identification of a phase transition between plastic flow and flux flow regimes.

Abstract

We study the dynamics of Josephson junction arrays with positional disorder and driven by an external current. We consider weak magnetic fields, corresponding to a frustration $f=n+1/25$ with $n$ integer. We find that above the critical current $i_c$ there is a plastic flow of vortices, where most of the vortices are pinned and only a few vortices flow through channels. This dynamical regime is characterized by strong fluctuations of the total vorticity. The number of the flow channels grow with increasing bias current. At larger currents there is a dynamical regime characterized by the homogeneous motion of all the vortices, i.e. a flux flow regime. We find a dynamical phase transition between the plastic flow and the flux flow regimes when analyzing voltage-voltage correlation functions.