Controlling persistent currents in fermionic rings via phase imprinting

Here I report on our recent results on exciting persistent currents in ring-shaped atomic Fermi superfluids. By employing a phase imprinting technique, we populate finite and controllable circulation states throughout the BEC-BCS crossover. We make use of a second disk condensate as a local oscillator to extract the circulation state of the ring by means of an interferometric probe, which allows us to monitor the current in time. By increasing the number of phase imprinting pulses, we are able to deterministically populate high circulation states of the fermionic ring superfluids, which are observed to be as long lived as the atomic sample. Finally, we induce the current decay by inserting a defect inside the ring trap to trigger dissipation. In the BEC and BCS regime, the high circulation currents are observed to decay via the emission of vortices, in well agreement with Gross-Pitaevskii numerical simulation for the first case. On the other hand, in the UFG all the accessible circulation states are found to be robust against dissipation. Our work demonstrates phase imprinting as a powerful technique to control the circulation state of a superfluid, opening for further studies on superfluidity and dissipation of strongly-interacting fermions.