Elementary Excitations of Antiferromagnetic Spin-1 Bosons in an Optical Lattice
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We study elementary excitations of spin-1 bosons with antiferromagnetic interaction in an optical lattice by applying the Gutzwiller approximation to the spin-1 Bose-Hubbard model. There appear various excitations associated with spin degrees of freedom in the Mott-insulator (MI) phase as well as in the superfluid (SF) phase. In this system, the ground state in the MI phase is known to exhibit a remarkable effect of even-odd parity of particle filling, in which even fillings stabilize the MI state due to formation of spin-singlet pairs. We find that excitation spectra in the MI phase exhibit characteristic features that reflect the even-odd parity effect of the ground state. We clarify evolution of elementary excitations across the quantum critical point of the SF-MI transition.
KeywordsSpin-1 boson SF-MI transition Elementary excitation
We thank D. Yamamoto, I. Danshita, M. Kunimi, Y. Kato, and T. Kimura for helpful discussions. S.T. was supported by Grant-in-Aid for Scientific Research, No. 24740276.
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