Deterministic Josephson Vortex Ratchet with a load

TL;DR

This paper experimentally studies a Josephson vortex ratchet that uses an asymmetric potential to direct fluxon movement, demonstrating its load capacity, power output, and efficiency, supported by a simple analytical model.

Contribution

It introduces an experimental investigation of a deterministic Josephson vortex ratchet with load capabilities and provides an analytical model for its performance metrics.

Findings

Measured the bias current at fluxon stopping point to evaluate ratchet strength

Estimated the ratchet's loading capacity, output power, and efficiency

Validated the simple model with experimental data

Abstract

We investigate experimentally a deterministic underdamped Josephson vortex ratchet -- a fluxon-particle moving along a Josephson junction in an asymmetric periodic potential. By applying a sinusoidal driving current one can compel the vortex to move in a certain direction, producing average dc voltage across the junction. Being in such a rectification regime we also load the ratchet, i.e., apply an additional dc bias current I_dc (counterforce) which tilts the potential so that the fluxon climbs uphill due to the ratchet effect. The value of the bias current at which the fluxon stops climbing up defines the strength of the ratchet effect and is determined experimentally. This allows us to estimate the loading capability of the ratchet, the output power and efficiency. For the quasi-static regime we present a simple model which delivers simple analytic expressions for the above mentioned figures of merit.