Current-induced vortex dynamics in Josephson-junction arrays: Imaging experiments and model simulations

TL;DR

This study combines imaging experiments and model simulations to analyze current-induced vortex dynamics in Josephson-junction arrays, revealing three distinct dynamic regimes as current increases.

Contribution

It provides a comparative analysis of experimental imaging and theoretical modeling to identify different vortex dynamic regimes in Josephson-junction arrays.

Findings

Identification of three distinct dynamic regimes with increasing bias current

Observation of vortex and antivortex motion in the vortex region

Linear current-voltage behavior at high currents

Abstract

We study the dynamics of current-biased Josephson-junction arrays with a magnetic penetration depth smaller than the lattice spacing. We compare the dynamics imaged by low-temperature scanning electron microscopy to the vortex dynamics obtained from model calculations based on the resistively-shunted junction model, in combination with Maxwell's equations. We find three bias current regions with fundamentally different array dynamics. The first region is the subcritical region, i.e. below the array critical current I_c. The second, for currents I above I_c, is a "vortex region", in which the response is determined by the vortex degrees of freedom. In this region, the dynamics is characterized by spatial domains where vortices and antivortices move across the array in opposite directions in adjacent rows and by transverse voltage fluctuations. In the third, for still higher currents, the dynamics is dominated by coherent-phase motion, and the current-voltage characteristics are linear.