Generic equilibration dynamics of planar defects in trapped atomic superfluids

Abstract

We investigate equilibration processes shortly after sudden perturbations are applied to ultracold trapped superfluids. We show the similarity of phase imprinting and localized density depletion perturbations, both of which initially are found to produce "phase walls". These planar defects are associated with a sharp gradient in the phase. Importantly they relax following a quite general sequence. Our studies, based on simulations of the complex time-dependent Ginzburg-Landau equation, address the challenge posed by these experiments: how a superfluid eventually eliminates a spatially extended planar defect. The processes involved are necessarily more complex than equilibration involving simpler line vortices. An essential mechanism for relaxation involves repeated formation and loss of vortex rings near the trap edge.

Phase slips in superconducting weak links

“…where Lη 1 = 0, Lη 2 = η 1 and L is the linear operator from (11). Using orthogonality conditions, we arrive at the coupled system…”

“…At very low temperatures, phase slips can be caused by quantum fluctuations (aptly called quantum phase slips) [3][4][5] . Phase slips are not unique to superconductors, they also occur in superfluid systems [6][7][8] , and more recently, dissipation due to phase slips were studied in cold atom systems [9][10][11] . In particular, phase slips can be triggered in a superfluid cold atom system by a rotating weak link 12 .…”

Cascade of Solitonic Excitations in a Superfluid Fermi gas: From Planar Solitons to Vortex Rings and Lines

“…Recently, several theoretical works have treated the evolution of fermionic superfluids following a phase imprint [21,23,33,34] and the possible cascade scenarios following the decay of a planar dark soliton [22,23,35,36] via various mean-field approaches. In some of these works, it has been numerically found that, in a cylindrically symmetric potential with negligible dissipation, a planar soliton decays into a vortex ring, which then undergoes a long-lived oscillatory motion along the z axis [22,35,36].…”

“…In some of these works, it has been numerically found that, in a cylindrically symmetric potential with negligible dissipation, a planar soliton decays into a vortex ring, which then undergoes a long-lived oscillatory motion along the z axis [22,35,36]. By mimicking experimental imperfections, such as trap distortions [21], and imperfect phase imprinting [23,34], later works found that the vortex ring further decays into a single remnant vortex. The proposed scenarios are, however, distinct from our observations.…”

Instabilities of the normal state in current-biased narrow superconducting strips

“…Note, that a realistic "onedimensional superconductor" is in fact a narrow strip with finite width W , much less than the Ginzburg-Landau coherence length ξ(τ ) ∝ (k B T c τ ) −1/2 , where τ = 1 − T /T c is the reduced temperature and T c the critical temperature. The energy dissipation in this system is related to phase-slip processes appearing in thin superconducting wires [4][5][6][7][8][9][10][11][12] or superfluids [13][14][15] , i.e., the processes of vortices/flux quanta crossing the strip.…”