The Bose-Hubbard model describing interacting bosons in an optical lattice is reduced to a simple spin-1 XY model with single-ion anisotropy in the vicinity of the Mort phase. We propose a mean-field theory based on a...The Bose-Hubbard model describing interacting bosons in an optical lattice is reduced to a simple spin-1 XY model with single-ion anisotropy in the vicinity of the Mort phase. We propose a mean-field theory based on a constraint SU(3) pseudo-boson representation on the effective model to study the properties of the superfluid-Mott-insulator phase transition. By calculating the elementary excitation spectra and the average particle number tluctuation in the Brillouin zone center, we lind that the energy gaps vanish continuously around (JXY/Jz)c≈ 0.175 and (JxY/Jz)c ≈ 0.094 for 2D and 3D cubic lattices respectively, where the superfluid order parameters come up from zero and the Mort insulator state changes into a superfluid state.展开更多
文摘The Bose-Hubbard model describing interacting bosons in an optical lattice is reduced to a simple spin-1 XY model with single-ion anisotropy in the vicinity of the Mort phase. We propose a mean-field theory based on a constraint SU(3) pseudo-boson representation on the effective model to study the properties of the superfluid-Mott-insulator phase transition. By calculating the elementary excitation spectra and the average particle number tluctuation in the Brillouin zone center, we lind that the energy gaps vanish continuously around (JXY/Jz)c≈ 0.175 and (JxY/Jz)c ≈ 0.094 for 2D and 3D cubic lattices respectively, where the superfluid order parameters come up from zero and the Mort insulator state changes into a superfluid state.