Superfluid-insulator transition of ultracold bosons in an optical lattice in the presence of a synthetic magnetic field
Indian Institute of Science Education and Research-Kolkata - Mohanpur, Nadia 741252, India
2 Theoretical Physics Division, Indian Association for the Cultivation of Sciences - Kolkata-700032, India
Accepted: 21 January 2011
We study the Mott-insulator–superfluid transition of ultracold bosonic atoms in a two-dimensional square optical lattice in the presence of a synthetic magnetic field with p/q (p and q being co-prime integers) flux quanta passing through each lattice plaquette. We show that on approach to the transition from the Mott side, the momentum distribution of the bosons exhibits q precursor peaks within the first magnetic Brillouin zone. We also provide an effective theory for the transition and show that it involves q interacting boson fields. We construct, from a mean-field analysis of this effective theory, the superfluid ground states near the transition and compute, for q=2, 3, both the gapped and the gapless collective modes of these states. We suggest experiments to test our theory.
PACS: 03.75.Lm – Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations / 05.30.Jp – Boson systems / 05.30.Rt – Quantum phase transitions
© EPLA, 2011