Rotating spin-1/2 Bose–Einstein condensates in a gradient magnetic field with spin–orbit coupling

Abstract

We study the ground-state phases of two-dimensional rotating spin–orbit coupled spin-1/2 Bose–Einstein condensates (BECs) in a gradient magnetic field. The competition between gradient magnetic field, spin–orbit coupling and rotation leads to a variety of ground-state phase structures. In the weakly rotation regime, as the increase of gradient magnetic field strength, the BECs experiences a phase transition from the unstable phase to the single vortex-line phase. The unstable phase presents the vortex lines structures along the off-diagonal direction. With magnetic field gradient strength increasing, the number of vortex lines changes accordingly. As the magnetic field gradient strength increases further, the single vortex-line phase with a single vortex line along the diagonal direction is formed. The phase diagram shows that the boundary between the two phases is linear with the relative repulsion λ ≥ 1 and is nonlinear with λ < 1. In the relatively strong rotation regime, in addition to the unstable phase and the single vortex-line phase, the vortex-ring phase is formed for the strong magnetic field gradient and rapid rotation. The vortex-ring phase shows the giant and hidden vortex structures at the center of ring. The strong magnetic field gradient makes the number of the vortices around the ring unchanged.

Vortex chains induced by anisotropic spin–orbit coupling and magnetic field in spin-2 Bose-Einstein condensates

“…[28] Various nontrivial excitations, i.e., strip phase and vortex-ring phase, have been investigated with the combined effects of rotation, magnetic field or isotropic SOC in the low-spin systems. [40,41] However, the exotic vortex configurations in the ferromagnetic phase, anti-ferromagnetic phase or the cyclic phase of the spin-2 BECs system remain unclear.…”