Persistent currents in rings of ultracold fermionic atoms

TL;DR

This paper demonstrates the creation and stability of persistent supercurrents in ultracold fermionic atom rings, showing their potential for matter-wave circuits and revealing robustness of superflow reappearance across interaction regimes.

Contribution

It reports the first observation of long-lived persistent currents in strongly-interacting ultracold fermionic rings and explores their stability and reappearance mechanisms.

Findings

Persistent currents last over 10 seconds in the strongly-interacting regime.

Superflow reappears after normal phase transition, insensitive to time and interaction strength.

Results suggest weak damping of normal currents enables superflow reemergence.

Abstract

We have produced persistent currents of ultracold fermionic atoms trapped in a ring, with lifetimes greater than 10 seconds in the strongly-interacting regime. These currents remain stable well into the BCS regime at sufficiently low temperature. We drive a circulating BCS superfluid into the normal phase and back by changing the interaction strength and find that the probability for quantized superflow to reappear is remarkably insensitive to the time spent in the normal phase and the minimum interaction strength. After ruling out spontaneous current formation for our experimental conditions, we argue that the reappearance of superflow is due to weak damping of normal currents in this limit. These results establish that ultracold fermionic atoms with tunable interactions can be used to create matter-wave circuits similar to those previously created with weakly-interacting bosonic atoms.