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Josephson dynamics in two-dimensional ring-shaped condensates

Koon Siang Gan1,*,†, Vijay Pal Singh2,*, Luigi Amico2,3,4, and Rainer Dumke5,6

  • *These authors contributed equally to this work.
  • †Contact author: ksgan1@e.ntu.edu.sg

Phys. Rev. Research 8, 023190 – Published 20 May, 2026

DOI: https://doi.org/10.1103/3249-x994

Abstract

We investigate Josephson transport in a fully closed, two-dimensional superfluid circuit formed by a ring-shaped Rb87 Bose-Einstein condensate that contains two optical barriers acting as movable weak links. Translating these barriers at controlled speeds imposes a steady bias current, enabling direct mapping of the current-chemical-potential (I−Δμ) characteristics. For narrow junctions (w≈1µm), the circuit exhibits a pronounced dc branch that terminates at a critical current Ic=9(1)×103s−1; above this threshold, the system switches to an ac, resistive regime. Classical-field simulations that include the moving barriers quantitatively reproduce both the nonlinear I−Δμ curve and the measured Ic, validating the underlying microscopic picture. Analysis of the ensuing phase dynamics shows that dissipation is mediated by the nucleation and traversal of vortex-antivortex pairs through the junctions, while the bulk condensate remains globally phase locked—direct evidence of the ring's topological constraint enforcing quantized circulation. These results establish a cold-atom analog of a superconducting quantum interference device in which Josephson dynamics can be resolved at the single-vortex level, providing a versatile platform for atomtronic circuit elements, nonreciprocal Josephson devices, and on-chip Sagnac interferometers for multiaxis rotation sensing.

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