The ground-state properties of neutral hard-core bosons trapped in an optical two-leg ladder in the presence of an artificial magnetic field are studied. For a weak field, two separated peaks appear in the momentum distribution as a signature of the Meissner state in which bosons, carrying persistent currents on each leg, condense into finite-momentum states, while for a strong field, a central peak and tiny bumps associated with the vortex lattice structure indicate that the ground state is the vortex state.

We investigate the momentum distribution associated with quantum phase transitions between a superfluid and a charge-density-wave state in the one-dimensional hard-core extended boson Hubbard model at half filling by using the Lanczos exact diagonalization method. The momentum distribution shows distinct features in different regions. At the Heisenberg point, it shows a universal behavior. In the superfluid phase, the Luttinger-liquid parameters are easily obtained from the finite-size scaling behaviors of the zero-momentum occupancy. Also the signature of a charge-density wave can be identified in the insulating phase.

No abstract

No abstract