Dynamics of vortex formation in merging Bose-Einstein condensate fragments

Abstract

We study the formation of vortices in a Bose-Einstein condensate (BEC) that has been prepared by allowing isolated and independent condensed fragments to merge together. We focus on the experimental setup of Scherer et al. [Phys. Rev. Lett. 98, 110402 (2007)], where three BECs are created in a magnetic trap that is segmented into three regions by a repulsive optical potential; the BECs merge together as the optical potential is removed. First, we study the two-dimensional case, in particular we examine the effects of the relative phases of the different fragments and the removal rate of the optical potential on the vortex formation. We find that many vortices are created by instant removal of the optical potential regardless of relative phases, and that fewer vortices are created if the intensity of the optical potential is gradually ramped down and the condensed fragments gradually merge. In all cases, self-annihilation of vortices of opposite charge is observed. We also find that for sufficiently long barrier ramp times, the initial relative phases between the fragments leave a clear imprint on the resulting topological configuration. Finally, we study the three-dimensional system and the formation of vortex lines and vortex rings due to the merger of the BEC fragments; our results illustrate how the relevant vorticity is manifested for appropriate phase differences, as well as how it may be masked by the planar projections observed experimentally.

Nonlinear waves in Bose–Einstein condensates: physical relevance and mathematical techniques

“…It is also possible to nucleate vortices by dragging a moving impurity through the condensate for speeds above a critical velocity (depending on the local density and also the shape of the impurity) [352][353][354][355][356][357][358][359]. Yet another possibility to nucleate vortices can be achieved by separating the condensate in different fragments and allowing them to collide [360][361][362]. The profile of a vortex in a two dimensional setting (see left panel of Fig.…”

Flows with fractional quantum circulation in Bose-Einstein condensates induced by nontopological phase defects

“…In BECs, quantized vortices have been nucleated by a variety of innovative methods, such as direct phase imprint [4,5], rotation of the condensate traps [6][7][8][9], stirring the BECs with laser beams [10] or moving optical obstacles [11,12], decay of dark solitons [13,14], and merging isolated condensates [15]. The last method is particularly interesting since it provides a means to test the celebrated Kibble-Zurek mechanism [16,17]. This mechanism explains the formation of vortices following a rapid second-order phase transition as due to the merging of isolated superfluid domains with random relative phases [18,19].…”

Finite-temperature dynamics of matter-wave dark solitons in linear and periodic potentials: An example of an antidamped Josephson junction

“…A relevant-and analytically tractable-mean-field model that has recently gained attention in the study of temperatureinduced dissipation of dark solitons [18,20,[22][23][24][25] is the so-called dissipative Gross-Pitaevskii equation (DGPE). This model, which was first introduced phenomenologically [26] and later was justified from a microscopic perspective [27], has also been used in other works to describe, e.g., decoherence [28] and growth [29] of BECs, damping of collective excitations of BECs [30], vortex lattice growth [31,32], vortex dynamics [33][34][35][36], and dynamics of quasicondensates [37]. In the case of dark solitons, the DGPE model can describe accurately finite-temperature-induced soliton decay: results stemming from a perturbative study of soliton dynamics in the framework of the DGPE, compares favorably to ones obtained by the more accurate stochastic Gross-Pitaevskii model [20,22,23] (the latter, is a grand-canonical theory of thermal BECs, containing damping and noise terms which describe interactions of low-energy atoms with a high-energy thermal reservoir-see, e.g., Refs.…”