Critical Transport and Vortex Dynamics in a Thin Atomic Josephson Junction

Abstract

We study the onset of dissipation in an atomic Josephson junction between Fermi superfluids in the molecular Bose-Einstein condensation limit of strong attraction. Our simulations identify the critical population imbalance and the maximum Josephson current delimiting dissipationless and dissipative transport, in quantitative agreement with recent experiments. We unambiguously link dissipation to vortex ring nucleation and dynamics, demonstrating that quantum phase slips are responsible for the observed resistive current. Our work directly connects microscopic features with macroscopic dissipative transport, providing a comprehensive description of vortex ring dynamics in three-dimensional inhomogeneous constricted superfluids at zero and finite temperatures. arXiv:1905.08893v2 [cond-mat.quant-gas]

Critical Josephson current in BCS-BEC–crossover superfluids

“…5 clearly demonstrates that our model is able to reproduce the results obtained in the literature so far with remarkable accuracy for all interactions and barrier heights. In particular, we emphasize that our analytic theory quantitatively matches the ETFM numerical results (green triangles) [46] obtained in the BEC limit even for barrier heights as low as V 0 /µ 0 ∼ 0.7, i.e. even when a sizable part of the trapped sample is out of the tunneling regime.…”

“…Building on a microscopic model for the Josephson current between two weakly interacting Bose Einstein condensates [12], we have developed a simple theoretical framework which captures the corresponding dynamics of strongly interacting fermionic superfluids throughout the BCS-BEC crossover. As testified by the comparison with available numerical [26,46] and experimental [30] data, our model provides a quantitative description of the critical currents in generic junction geometries, solely based on bulk properties of the superfluid state and the knowledge of the single boson transmission amplitude. An important feature of our theory is that it provides a consistent explanation for the non-monotonic trend for the maximum Josephson current observed near unitarity.…”

“…Finally, we compare our model predictions with experimental data that were obtained in the Lithium lab at LENS [30], and also with ETFM numerical simulations carried out in the BEC limit [46]. To this end, we evaluate the maximum Josephson current I M ax accounting for both first and second order contributions [47], in the case of harmonically trapped samples and Gaussian barriers (see Fig.…”

“…[30], measured as a function of V0/µ0 for 6 Li fermionic superfluids at unitarity, in the BEC and BCS limit (see legend), are compared with our model predictions (solid lines), employing the µB and nc trends obtained in the Luttinger-Ward approach [43,51]. In the BEC limit, our results are also compared with EFTM simulations [46] (green triangles). Trap frequencies and atom number were fixed to their mean values in the experiment (nominal value in the simulation).…”

“…(3). Moreover, in order to test the predictions of our model against recent experimental data [30] and BEC results of EFTM numerical simulations [46] available in the literature, it is necessary to generalize the results obtained in Eq. (3) to the experimentally relevant case [29,30] of inhomogeneous samples and Gaussian barriers, see Fig.…”