Two-Fluxon Dynamics in Annular Josephson Junction

TL;DR

This paper investigates the dynamics of two fluxons in an annular Josephson junction under external magnetic fields through analytical, numerical, and experimental methods, providing new insights into fluxon interactions and motion.

Contribution

It presents an analytical expression for fluxon interaction potential at arbitrary velocities and derives equations of motion treating fluxons as quasi-particles.

Findings

Analytical potential expression matches numerical simulations

Numerical results agree with experimental data

Fluxon dynamics are well-described by the derived equations

Abstract

Two-fluxon state in an annular Josephson junction in the presence of external magnetic field is studied analytically, numerically and experimentally. We obtain an analytical expression for the potential of interaction between the fluxons moving at arbitrary velocities (without the use of the "nonrelativistic" approximation). Treating the fluxons as quasi-particles, we then derive equations of motion for them. Direct simulations of the full extended sine-Gordon equation are in good agreement with results produced by the analytical model, in a relevant parameter region. Experimental data qualitatively agree with the numerical results.