Spinor Bose-Einstein Condensates with Many Vortices

Vortex-lattice structures of antiferromagnetic spinor Bose-Einstein condensates with hyperfine spin F=1 are investigated theoretically based on the Ginzburg-Pitaevskii equations near $T_{c}$. The Abrikosov lattice with clear core regions are found {\em never stable} at any rotation drive $\Omega$. Instead, each component $\Psi_{i}$ $(i=0,\pm 1)$ prefers to shift the core locations from the others to realize almost uniform order-parameter amplitude with complicated magnetic-moment configurations. This system is characterized by many competing metastable structures so that quite a variety of vortices may be realized with a small change in external parameters.