Novel phases in quantum frustrated magnetic systems
Guang-Ming Zhang
Department of Physics, Tsinghua University, Beijing, 100084, P.R. China
We consider the superfluid-Mott insulating phase transition of ultracold boson atoms in optical lattices by focusing on the effective model in the Mott insulating phase with odd number of spin-1 bosons. In terms of an SU(3) boson representation, a valence bond mean field theory is developed. In 1D, a first-order quantum phase transition from a spin singlet to a quadrupole phase with gapful excitations is identified, while on a 2D square lattice a quadrupolar ordering phase with gapless excitations always prevails. In both 1D and 2D cases, we find that the spin structure factor displays dominant antiferromagnetic fluctuations, while the quadrupolar structure factor exhibits strong ferroquadrupolar correlations.