Characterising chaotic dynamics of quantum vortices in Bose-Einstein condensates

서상원

Alexander L. Fetter

Tiantian Zhang, James Schloss, Andreas M. D. Thomasen +3 more

We investigate a small vortex-lattice system of four corotating vortices in an atomic Bose-Einstein condensate and find that the vortex dynamics display chaotic behavior after a system quench introduced by reversing the direction of circulation of a single vortex through a phase-imprinting process. By tracking the vortex trajectories and Lyapunov exponent, we show the onset of chaotic dynamics is not immediate, but occurs at later times and is accelerated by the close approach and separation of all vortices in a scattering event. The techniques we develop could potentially be applied to create locally induced chaotic dynamics in larger lattice systems as a stepping stone to study the role of chaotic events in turbulent vortex dynamics.

Sergey K. Nemirovskii

A statement of the quantum turbulence problem in both a Bose – Einstein condensate (BEC) and superfluid helium is formulated. In superfluid helium use is made of a so-called vortex filament method, in which quantum vortices are represented by string-like objects, i.e. vortex lines. The dynamics of the vortex lines is determined by deterministic equations of motion, supplemented by random reconnections. Unlike He II, the laws of the dynamics of quantum vortices in BEC are based on the nonlinear Schrödinger equation. This makes it possible to obtain a microscopic description of the collision of vortices, the structure of a vortex filament, etc. A comparative analysis of these complementary approaches is carried out. It is shown that there are some features that do not automatically transfer the results obtained for BEC to vortices in He II and vice versa.

Sungjong Woo

Tiantian Zhang, James Schloss, Andreas Thomasen +3 more

A study of vortex dynamics in a confined superfluid shows that a system of three co-rotating quantum vortices and one vortex of opposite rotation exhibit chaotic dynamics. We find the onset of chaos is seeded through the close approach and separation of vortices in a scattering event.