We demonstrate that a spin-orbit-coupled Bose-Einstein condensate can be effectively rotated by adding a real magnetic field to inputting gauge angular momentum, which is distinctly different from the traditional ways of rotation by stirring or Raman laser dressing to inputting canonical angular momentum. The gauge angular momentum is accompanied by the spontaneous generation of equal and opposite canonical angular momentum in the ground states, and it leads to the nucleation of quantized vortices. We explain this by indicating that the effective rotation with the vortex nucleation results from the effective magnetic flux induced by the gauge potential, which is essentially different from the previous scheme of creating vortices by synthetic magnetic fields. In the weakly interacting regime, symmetrically placed domains separated by vortex lines as well as half-integer giant vortices are discovered. With relatively strong interatomic interaction, we predict a structure of coaxially arranged annular vortex arrays, which is in stark contrast to the familiar Abrikosov vortex lattice. The developed way of rotation may be extended to a more general gauge system.
Abstract The ground-state phases of Rashba spin–orbit (SO)-coupled Bose–Einstein condensates (BECs) in a quadrupole magnetic field are studied. The coupling of quadrupole magnetic field and spin induces local nonzero gauge particle current, accompanied by the generation of equal and opposite canonical particle current, and leads to the spontaneous nucleation of quantized vortices. The condensates exhibit a variety of rich density patterns and vortex arrangements resulting from the competition among quadrupole magnetic field, SO coupling, and interatomic interactions. Novel vortex structures, such as static vortex dipole, three-vortex molecule and the structure of a cross-arranged vortices and anti-vortices surrounded by a density annulus are found in the condensates. These structures greatly enrich the ground-state phases of SO-coupled BECs, and help to understand the superfluid behavior of a BEC and the nonlinear behavior of coherent matter waves.
Abstract We investigate ground-state phase diagram of helicoidal spin-orbit coupled Bose-Einstein condensates in a harmonic trap when the intraspecies interaction
g and the interspecies interaction
g↑↓ are unequal. In the case of
g>g↑↓, increasing the strength of the helicoidal spin-orbit coupling can induce a multiple-peak matter-wave structure with small oscillation amplitude. In the case of
g＜g↑↓, increasing the strength of the helicoidal spin-orbit coupling can induce a multiple-peak matter-wave structure with large oscillation amplitude. Our findings show that the helicoidal spin-orbit coupling plays a crucial role in inducing multiple-peak matter waves. Adjusting the spin-orbit coupling strength and the gauge potential can control the number of wave peaks. Finally, we also discuss the ground-state properties under different Zeeman splitting parameters when the helicoidal spin-orbit coupling strength and the gauge potential are fixed.