Dynamical excitations in the collision of two-dimensional Bose-Einstein condensates

Yang, Tao; Xiong, Bo; Benedict, K. A.

doi:10.1103/physreva.87.023603

Cited by 32 publications

(36 citation statements)

References 44 publications

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“…We note that the density wave oscillations are greater after the annihilation of vortex dipoles and the decay of the soliton ring, which indicates that the decay of vortex dipoles or soliton rings can make much severe excitations in dynamical systems. The revival of vortex dipoles can depress the excitations in the system as stated in refs 34 , 35 .…”

Section: Numerical Results and Analysismentioning

confidence: 98%

“…As the size of the vortex cores in a trapped condensate is ordinarily several times smaller than the wavelength of light used for imaging, in experiments the condensates are usually allowed to expand to a point at which the vortex cores are large compared to the imaging resolution 24 25 26 27 28 29 30 . Many works have been done to develop the vortex detection techniques and to understand vortex dynamics during the interference of BECs 25 31 32 33 34 35 36 , which is important for the applications of matter-wave interferometry. However, the direct, in situ observation of vortices in a trapped condensate without expansion was wachieved experimentally only in the past few decades.…”

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confidence: 99%

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Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates

Yang

Zou

et al. 2016

Sci Rep

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Dynamics of vortex clusters is essential for understanding diverse superfluid phenomena. In this paper, we examine the dynamics of vortex quadrupoles in a trapped two-dimensional (2D) Bose-Einstein condensate. We find that the movement of these vortex-clusters fall into three distinct regimes which are fully described by the radial positions of the vortices in a 2D isotropic harmonic trap, or by the major radius (minor radius) of the elliptical equipotential lines decided by the vortex positions in a 2D anisotropic harmonic trap. In the “recombination” and “exchange” regimes the quadrupole structure maintains, while the vortices annihilate each other permanently in the “annihilation” regime. We find that the mechanism of the charge flipping in the “exchange” regime and the disappearance of the quadrupole structure in the “annihilation” regime are both through an intermediate state where two vortex dipoles connected through a soliton ring. We give the parameter ranges for these three regimes in coordinate space for a specific initial configuration and phase diagram of the vortex positions with respect to the Thomas-Fermi radius of the condensate. We show that the results are also applicable to systems with quantum fluctuations for the short-time evolution.

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Section: Numerical Results and Analysismentioning

confidence: 98%

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confidence: 99%

Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates

Yang

Zou

et al. 2016

Sci Rep

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“…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]. In addition, understanding the processes involved in the merging of isolated condensates is also important for matter wave interferometry [20][21][22][23].…”

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confidence: 99%

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

2018

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It is a common view that rotational motion in a superfluid can exist only in the presence of quantized vortices. However, in our numerical studies on the merging of two concentric BoseEinstein condensates with axial symmetry in two-dimensional space, we observe the emergence of a spiral dark soliton when one condensate has a non-zero initial angular momentum. This spiral dark soliton enables the transfer of angular momentum between the condensates and allows the merged condensate to rotate even in the absence of quantized vortices. We examine the flow field around the soliton and reveal that its sharp endpoint can induce flow like a vortex point but with a fraction of a quantized circulation. This interesting nontopological "phase defect" may generate broad interests since rotational motion is essential in many quantum transport processes. The hydrodynamics of quantum fluids such as atomic Bose-Einstein condensates (BECs) and superfluid helium are strongly affected by quantum effects [1][2][3]. For instance, it is well-known that in a simply-connected quantum fluid, rotational motion can arise only through the formation of topological defects in the form of quantized vortices, each of which carries a circulation of κ = h/m, where h is Plancks constant and m is the mass of the particles that form the condensate. 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]. In addition, understanding the processes involved in the merging of isolated condensates is also important for matter wave interferometry [20][21][22][23].So far, many studies on condensate merging have focused on condensates with uniform initial phases. However, the situation is less clear when some condensates contain vortices and have non-uniform phases before merging occurs. Many interesting questions can be raised. For instance, how will the angular momentum be transferred from a rotating condensate to an initially static condensate? Can vortices form due to the veloc- * Email: wguo@magnet.fsu.edu ity gradient near the interface between condensates like that in classical shear flows? Is the angular momentum transfer always associated with vorticity transfer? To provide insights into these questions, we have studied a representative condensate configuration: the merging of a disc Bose-Einstein condensate with a concentric ring condensate in two-dimensional (2D) space, with one of them having a non-zero initial angular momentum induced by a vortex point at the center. We shall report in...

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“…As stated in Refs. [26,27], the initial displacement (∆ x , ∆ y ) of the condensates from the trap centre plays an important role in the interference process and formation of dynamical excitations. This also applies when we consider the interaction between condensate cloud and the barrier potential.…”

Section: Resultsmentioning

confidence: 99%

“…As the perfect initial dark-soliton structure (without some residual sound excitations) obtained by the imaginary time evolution may not be able to produce in experiments, we suggest to prepare these 2D configurations by combining condensates in a double well potential with phase imprinting technique as described in Ref. [26], where the created dark-soliton can also survive for 1.19T . We find that the orientation of the soliton affects the quantum reflection in a non-trivial way and the sensitivity of the reflection probability on the orientation of the soliton is significant.…”

Section: Discussionmentioning

confidence: 99%

Influence of a dark soliton on the reflection of a Bose–Einstein condensate by a square barrier

et al. 2018

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We study the quantum reflection of a two-dimensional disk-shaped Bose-Einstein condensate with a dark-soliton excitation by a square potential barrier. For the giving geometry, the dark-soliton initially located at the centre of the condensate cloud survive long enough for investigating the reflection process. We show the time evolution of the reflection probability with respect to various width of the barrier. The asymptotic value of the reflection probability is decreased by the existence of a dark-soliton, and is highly sensitive to the initial orientation of the dark-soliton which also affects the excitation properties during the process of condensate and barrier interaction.

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Dynamical excitations in the collision of two-dimensional Bose-Einstein condensates

Cited by 32 publications

References 44 publications

Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates

Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensates

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

Influence of a dark soliton on the reflection of a Bose–Einstein condensate by a square barrier

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