Shan Zou’s research while affiliated with Northwest University and other places

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Publications (3)


FIG. 1. (a) The density distribution of the condensate and the initial velocity field (red arrow) of the vortex dipole on the xOy plane. (b), (c) and (d) Isosurfaces of the density field at threshold level ρ th = 30 and the corresponding phase diagrams at various snapshots with the initial separation of the vortex lines being r jl = 4.0a 0 .
FIG. 4. The dynamics of a hopfion structure which is created by imprinting a central vortex line when the vortex ring forms shown at time 11.9t 0 -12.9t 0 (a), 10.4t 0 -11.4t 0 (b) and 9.4t 0 -10.4t 0 (c) and the time step dt = 0.2t 0 at threshold level ρ th = 30 correspond to Fig. 2(a)-(c). (d)-(f) are the Isosurface of the density field at threshold level ρ th = 20 at various time t = 12.9t 0 , t = 11.4t 0 and t = 10.4t 0 correspond to (a)-(c), respectively.
Formation of vortex rings and hopfions in trapped Bose–Einstein condensates
  • Article
  • Full-text available

February 2021

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139 Reads

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10 Citations

Shan Zou

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Wen-Kai Bai

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The topological transition of vortex lines to vortex rings and hopfions is numerically investigated by the Gross–Pitaevskii equation in three-dimensional trapped Bose–Einstein condensates. The shape of the vortex rings formed by the two vortex lines of the vortex dipole depends strongly on the initial separation of the lines. An approximately perfect vortex ring can be obtained by choosing some suitable values of the separation. The deformation of the formed rings depends on the shape of the rings in turn. Furthermore, we show a feasible approach to generate vortex hopfions by imprinting a vortex line in the center of the generated vortex rings. Specifically, the movement of the vortex rings can excite helical waves along the central vortex line of the hopfion structure if the vortex ring is not perfect.

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Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensate

September 2016

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.


Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensate

July 2016

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104 Reads

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18 Citations

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.

Citations (2)


... Optical hopfions are kinds of typical structured light with three-dimensional (3D) topological states. Because of the unique field profiles and particlelike properties, they have been explored in many physical fields, including high-energy physics [9], quantum fields [10,11], condensed matter physics [12][13][14][15], and cosmology [16,17]. Recently, photonic hopfions have been realized in free space [8,18,19]. ...

Reference:

Formation and Controlling of Optical Hopfions in High Harmonic Generation
Formation of vortex rings and hopfions in trapped Bose–Einstein condensates

... One can see that compared to vortex excitation, phonon excitation has little effect on the amplitude of oscillating atomic flow. The long-term evolution of η is not highly regular, as vortex pairs experience complex movement that induces density wave oscillations (sound waves) within the system [49][50][51][52]. ...

Dynamics of vortex quadrupoles in nonrotating trapped Bose-Einstein condensate