Vortex trapping in suddenly connected Bose-Josephson junctions

Abstract

We investigate the problem of vortex trapping in cyclically coupled Bose-Josephson junctions. Starting with $N$ independent BECs we couple the condensates through Josephson links and allow the system to reach a stable circulation by adding a dissipative term in our semiclassical equations of motion. The central question we address is what is the probability to trap a vortex with winding number $m$. Our numerical simulations reveal that the final distribution of winding numbers is narrower than the initial distribution of total phases, indicating an increased probability for no-vortex configurations. Further, the nonlinearity of the problem manifests itself in the somewhat counter-intuitive result that it is possible to obtain a non-zero circulation starting with zero total phase around the loop. The final width of the distribution of winding numbers for $N$ sites scales as $\lambda N^{\alpha}$, where $\alpha=0.47\pm 0.01$ and $\lambda <0.67$ (value predicted for the initial distribution) indicating a shrinking of the final distribution. The actual value of $\lambda$ is found to depend on the strength of dissipation.