Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (CNR-INO), 50019 Sesto Fiorentino, Italy.
European Laboratory for Nonlinear Spectroscopy (LENS), 50019 Sesto Fiorentino, Italy.
Science. 2020 Jul 3;369(6499):84-88. doi: 10.1126/science.aaz2463.
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.
直流约瑟夫森效应为研究超流序参量提供了一种对相位敏感的工具。我们报告了在没有外加电势差的情况下，通过隧道势垒观察到强相互作用费米流体中的直流约瑟夫森超导电流。对于足够强的势垒，我们观察到了与约瑟夫森开创性预测一致的正弦电流-相位关系。我们绘制了零电阻状态及其随结参数的破坏图，提取了约瑟夫森临界电流行为。通过将我们的结果与解析模型进行比较，我们确定了整个 Bardeen-Cooper-Schrieffer-Bose-Einstein 凝聚交叉区域的配对凝聚分数。我们的工作表明，相干约瑟夫森输运可用于确定不同原子系统中的超流序参量，即使在存在强关联的情况下也是如此。
