Ratchet-like dynamics of fluxons in annular Josephson junctions driven by bi-harmonic microwave fields

TL;DR

This paper reports the experimental observation of unidirectional fluxon motion in an annular Josephson junction driven by a bi-harmonic microwave field, confirming theoretical predictions of ratchet-like dynamics.

Contribution

It provides the first experimental evidence of fluxon ratchet behavior driven by bi-harmonic forces in Josephson junctions, aligning with theoretical models.

Findings

Fluxon velocity depends on phase shift between harmonics

Unidirectional fluxon motion observed at zero dc bias

Results agree qualitatively with theoretical expectations

Abstract

Experimental observation of the unidirectional motion of a topological soliton driven by a bi-harmonic ac force of zero mean is reported. The observation is made by measuring the current-voltage characteristics for a fluxon trapped in an annular Josephson junction that was placed into a microwave field. The measured dependence of the fluxon mean velocity (rectified voltage) at zero dc bias versus the phase shift between the first and second harmonic of the driving force is in qualitative agreement with theoretical expectations.