Staggered-vortex superfluid of ultracold bosons in an optical lattice.
We show that the dynamics of cold bosonic atoms in a two-dimensional square optical lattice produced by a bichromatic light-shift potential is described by a Bose-Hubbard model with an additional effective staggered magnetic field. In addition to the known uniform superfluid and Mott insulating phases, the zero-temperature phase diagram exhibits a novel kind of finite-momentum superfluid phase, characterized by a quantized staggered rotational flux. An extension for fermionic atoms leads to an anisotropic Dirac spectrum, which is relevant to graphene and high-T(c) superconductors.
Institute for Theoretical Physics, Utrecht University, 3508 TD Utrecht, The Netherlands.
Lih-King
LK
Lim
C Morais
CM
Smith
Andreas
A
Hemmerich