Fluxon-semifluxon interaction in an annular long Josephson 0-pi-junction

TL;DR

This paper theoretically studies the interaction between fluxons and semifluxons in an annular Josephson junction, revealing how current-voltage measurements can determine semifluxon polarity and analyzing fluxon pinning.

Contribution

It introduces a theoretical analysis of fluxon-semifluxon interactions in an annular junction with a single $ ext{ extpi}$-discontinuity, including stability and depinning current calculations.

Findings

Current-voltage characteristics reveal semifluxon polarity.

Static configurations can be stable or unstable depending on fluxon and semifluxon polarity.

Calculated depinning currents for fluxons pinned by fractional vortices.

Abstract

We investigate theoretically the interaction between integer and half-integer Josephson vortices (fluxons and semifluxons) in an annular Josephson junction. Semifluxons usually appear at the 0-$\pi$-boundary where there is a $\pi$-discontinuity of the Josephson phase. We study the simplest, but the most interesting case of one $\pi$-discontinuity in a loop, which can be created only artificially. We show that measuring the current-voltage characteristic after injection of an integer fluxon, one can determine the polarity of a semifluxon. Depending on the relative polarity of fluxon and semifluxon the static configuration may be stable or unstable, but in the dynamic state both configurations are stable. We also calculate the depinning current of $N$ fluxons pinned by an arbitrary fractional vortex.