Observation of the twisted decay of quadruply charged vortices taking place in an atomic Bose–Einstein condensate. Numerical simulations show that the singly-charged vortices, resulting from the decay of a multi-charged vortex, twist around intertwined in the shape of helical waves.
Steps to reproduce
The multi-charged vortices are nucleated by adiabatically reducing and inverting the initial trap bias field from B0≈0.5G down to B0≈ −0.5G. The resulting magnetic field along the weak trap direction,z, axis is reversed during the process. During this adiabatic reversal process, the atomic spins are forced to follow the rotation taking place in the local field directions. The magnetic field reversal rate is slow enough (0.1 G/ms) so that almost all the atomic spins adiabatically follow the magnetic field directions, under our typical experimental conditions. Also, since the direction of the rotation depends on the spatial position of each atom, the atom acquires a different topological phase depending on its position. The spin reversal results in the phase winding in the condensate order parameter with 4πhbar per atom, corresponding to a n= 4 charge vortex imprinted on the BEC. Finally, this process works well though it induces significant loss of atoms (50%) during the zero crossing, due to the Majorana flips, which is consistent with previous studies.