Transition from phase slips to the Josephson effect in a superfluid 4He weak link

TL;DR

This study measures the current-phase relation in superfluid 4He weak links, revealing a transition from phase slip dynamics to Josephson effect behavior as coupling strength varies, indicating potential for superfluid helium devices.

Contribution

First experimental observation of the transition from phase slip to Josephson effect in superfluid 4He weak links by measuring the current-phase relation.

Findings

Transition from phase slip to Josephson regime observed

Current-phase relation changes from linear to sinusoidal

Potential for superfluid helium device development

Abstract

The rich dynamics of flow between two weakly coupled macroscopic quantum reservoirs has led to a range of important technologies. Practical development has so far been limited to superconducting systems, for which the basic building block is the so-called superconducting Josephson weak link. With the recent observation of quantum oscillations in superfluid 4He near 2K, we can now envision analogous practical superfluid helium devices. The characteristic function which determines the dynamics of such systems is the current-phase relation Is(phi), which gives the relationship between the superfluid current Is flowing through a weak link and the quantum phase difference phi across it. Here we report the measurement of the current-phase relation of a superfluid 4He weak link formed by an array of nano-apertures separating two reservoirs of superfluid 4He. As we vary the coupling strength between the two reservoirs, we observe a transition from a strongly coupled regime in which Is(phi) is linear and flow is limited by 2pi phase slips, to a weak coupling regime where Is(phi) becomes the sinusoidal signature of a Josephson weak link.