Quantum ratchet effect for vortices

TL;DR

This paper demonstrates a quantum ratchet effect for vortices in a Josephson junction array, showing how the engineered potential energy landscape influences vortex transport and rectification at quantum scales.

Contribution

It introduces a method to design vortex band structures in solid-state devices to control quantum ratchet effects, revealing the role of potential asymmetry in vortex transport.

Findings

Quantum ratchet effect observed in vortex motion.

Asymmetric structures with one band below the barrier do not show rectification.

Voltage-current characteristics follow universal or non-universal power laws.

Abstract

We have measured a quantum ratchet effect for vortices moving in a quasi-one-dimensional Josephson junction array. In this solid-state device the shape of the vortex potential energy, and consequently the band structure, can be accurately designed. This band structure determines the presence or absence of the quantum ratchet effect, as observed in the presented experiments. In particular, asymmetric structures possessing only one band below the barrier do not exhibit current rectification at low temperatures and bias currents. The quantum nature of transport is also revealed in a universal/non-universal power-law dependence of the measured voltage-current characteristics for samples without/with rectification.