Fluxon mobility in an asymmetric SQUID array

TL;DR

This paper studies fluxon movement in an asymmetric SQUID array using the discrete double sine-Gordon model, revealing specific velocities with stable fluxon propagation and their impact on current-voltage characteristics.

Contribution

It introduces a detailed analysis of fluxon velocities and their effects in an asymmetric SQUID array modeled by the discrete double sine-Gordon equation, highlighting new velocity regimes and depinning phenomena.

Findings

Existence of finite fluxon velocities with stable propagation

Identification of voltage gaps in current-voltage characteristics

Minimum critical depinning current at specific asymmetry ratios

Abstract

Fluxon dynamics in the dc-biased array of asymmetric three-junction superconducting quantum interference devices (SQUIDs) is investigated. The array of SQUIDs is described by the discrete double sine-Gordon equation. It appears that this equation possesses a finite set of velocities at which the fluxon propagates with the constant shape and without radiation. The signatures of these velocities appear on the respective current-voltage characteristics of the array as inaccessible voltage intervals (gaps). The critical depinning current has a clear minimum as a function of the asymmetry parameter (the ratio of the critical currents of the left and right junctions of the SQUID), which coincides with the minimum of the Peierls-Nabarro potential.