Strongly correlated superfluid order parameters from dc Josephson supercurrents

Year: 2020

Authors: Kwon WJ., Del Pace G., Panza R., Inguscio M., Zwerger W., Zaccanti M., Scazza F., Roati G.

Autors Affiliation: Consiglio Nazl Ric CNR INO, Istituto Nazionale di Ottica, I-50019 Sesto Fiorentino, Italy; European Lab Nonlinear Spect LENS, I-50019 Sesto Fiorentino, Italy; Univ Florence, Dept Phys & Astron, I-50019 Sesto Fiorentino, Italy; Campus Biomed Univ Rome, Dept Engn, I-00128 Rome, Italy; Tech Univ Munich, Phys Dept, D-85747 Garching, Germany

Abstract: The direct-current (dc) Josephson effect provides a phase-sensitive tool for investigating superfluid order parameters. We report on the observation of dc Josephson supercurrents in strongly interacting fermionic superfluids across a tunneling barrier in the absence of any applied potential difference. For sufficiently strong barriers, we observed a sinusoidal current-phase relation, in agreement with Josephson’s seminal prediction. We mapped out the zero-resistance state and its breakdown as a function of junction parameters, extracting the Josephson critical current behavior. By comparing our results with an analytic model, we determined the pair condensate fraction throughout the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover. Our work suggests that coherent Josephson transport may be used to pin down superfluid order parameters in diverse atomic systems, even in the presence of strong correlations.

Journal/Review: SCIENCE

Volume: 369      Pages from: 84  to: 87

More Information: Supported by European Research Council GA no. 307032 QuFerm2D and no. 637738 PoLiChroM, Fondazione Cassa di Risparmio di Firenze project QuSim2D 2016.0770, and European Union´s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie GAs no. 705269 and no. 843303.
DOI: 10.1126/science.aaz2463

Citations: 49
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