Phase Fluctuations in Concentric Rings of Fermionic Superfluid

Fluctuations are enhanced in low-dimensional systems, and in highly elongated superfluid systems, phase fluctuations are expected to cause power-law decay of long range order. We have investigated the effects of phase fluctuations in rings of ultracold fermionic superfluids, particularly how they affect preparation and deterministic control of quantized circulation states. We have observed increasing thermal phase fluctuations in narrow superfluid rings as the effective transverse width is decreased. In addition to the evidence of changing thermal correlation length within each ring, we also see a reduction in the strength of fluctuations when there is sufficiently strong coherent coupling between concentric rings.