Superfluid–Mott Insulator Transition of Spinor Bose Gases with External Magnetic Fields

Abstract

We study the superfluid–Mott insulator (SF–MI) transition of a spin-1 boson system in an optical lattice, especially the responce of the system to an external magnetic field. Using the mean field theory, we obtain the phase diagram of SF–MI transition at zero temperature. For antiferromagnetic bosons, the Mott insulator region is stabilized when the number of particles per site is even. We find that only by changing the external magnetic field, the SF–MI transition is realized. On the other hand, the ferromagnetic case perfectly recovers the spin frozen case, that is already performed in experiments.