Half-quantum-vortex generation in a two-component Bose-Einstein condensate by an oscillatory magnetic obstacle

We numerically investigate the dynamics of vortex generation in a two-dimensional, two-component BoseEinstein condensate subjected to an oscillatory magnetic obstacle. The obstacle creates both repulsive and attractive Gaussian potentials for the two symmetric spin-t and 4 components, respectively. We demonstrate that, as the oscillating frequency f increases, two distinct critical dynamics arise in the generation of halfquantum vortices (HQVs) with different spin circulations. Spin-t vortices are nucleated directly from the moving obstacle at low f, while the spin-,[ vortices are created at high f by breaking a spin wave pulse in front of the obstacle. We find that vortex generation is suppressed for sufficiently weak obstacles, in agreement with recent experimental results by Kim et al. [Phys. Rev. Lett. 127, 095302 (2021)]. This suppression is caused by the finite sweeping distance of the oscillating obstacle and the reduction in friction in a supersonic regime. Finally, we show that the characteristic length scale of the HQV generation dynamics is determined by the spin healing length of the system.

Automated summary

We numerically investigate the dynamics of vortex generation in a two-dimensional, two-component Bose-Einstein condensate subjected to an oscillatory magnetic obstacle. We find that vortex generation exhibits two distinct critical dynamics with different spin circulations as the oscillating frequency increases. We also observe that vortex generation is suppressed for weak obstacles, in agreement with recent experimental results. The characteristic length scale of the vortex generation dynamics is determined by the spin healing length of the system.