Vortex nucleation in Bose–Einstein condensates confined in a QUIC trap by topological phase imprinting

We studied the nucleation of quadruple-quantized vortices in Bose–Einstein condensates confined in a quadrupole-Ioffe-configuration (QUIC) magnetic trap by means of the topological phase imprinting method, wherein the initially aligned atomic spins were adiabatically reversed by applying an external bias magnetic field. We calculated the change in the magnetic field distributions of the trap when a homogeneous or a gradient bias field was applied for reversing the spins, and almost the same results were obtained for both cases. We applied the gradient bias field using a single coil because of its simplicity and stability. Vortices were successfully created at the reversal time of atomic spins between 2 and 16 ms. Moreover, the vortices were observed at a holding time of up to 9 ms in the magnetic trap after a constant reversal time of 5 ms.