Tuesday, June 11, 2013

1306.2147 (Y. Kuno et al.)

Two-species repulsive bosons in an optical lattice: Phase diagram, the
Nambu-Goldstone bosons, the Higgs mode and vortex lattice

Y. Kuno, K. Suzuki, I. Ichinose
In the previous papers, we studied the bosonic t-J mode and derived an effective field theory, which is a kind of quantum XY model. The bosonic t-J model is expected to be realized by experiments of two-component cold atoms in an optical lattice. In this paper, we consider a similar XY model that describes phase diagram of the t-J model with a mass difference. Phase diagram and critical behavior of the quantum XY model are clarified by means of the Monte-Carlo simulations. Effective field theory that describes the phase structure and low-energy excitations of the quantum XY model is derived. Nambu-Goldstone bosons and the Higgs mode are investigated by using the effective field theory. We also investigate physical properties of the quantum XY model in an effective magnetic field that is realized by rotating the optical lattice. We show that low-energy states of the system strongly depend on the magnitude of the "magnetic field". For some specific values of the magnetic field, vortex lattice forms and the correlation function of the bosons exhibits solid like behavior, which is a kind of Bose-Einstein condensation.
View original: http://arxiv.org/abs/1306.2147

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