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Superfluid-Mott-Insulator Phase Transition and Collective Fluctuations in both Phases of Bosons in an Optical Lattice |
| ZHU Rui |
| Department of Physics, Tsinghua University, Beijing 100084 |
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| Cite this article: |
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ZHU Rui 2007 Chin. Phys. Lett. 24 797-799 |
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Abstract 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 Mott phase. In the strong coupling Mott insulating regime, we propose a mean field theory based on a constraint SU(3) pseudo-boson representation on the effective model and discuss the excitation spectra and the phase transition to the superfluid state. Further to the superfluid phase, we use the coherent-state approach to derive the collective excitation modes. It is found that the Mott phase has two degenerate gapped quadratic excitation spectra which graduate into two degenerate gapless linear ones at the transition point, and one gapless linear mode with one gapped quadratic
mode in the superfluid phase.
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| Keywords:
67.40.Db
32.80.Pj
03.75.Lm
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Received: 20 September 2006
Published: 08 February 2007
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| PACS: |
67.40.Db
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32.80.Pj
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03.75.Lm
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(Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations)
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