33 research outputs found
Creating superfluid vortex rings in artificial magnetic fields
Artificial gauge fields are versatile tools that allow to influence the
dynamics of ultracold atoms in Bose-Einstein condensates. Here we discuss a
method of artificial gauge field generation stemming from the evanescent fields
of the curved surface of an optical nanofibre. The exponential decay of the
evanescent fields leads to large gradients in the generalized Rabi frequency
and therefore to the presence of geometric vector and scalar potentials. By
solving the Gross-Pitaevskii equation in the presence of the artificial gauge
fields originating from the fundamental HE mode of the fibre, we show
that vortex rings can be created in a controlled manner. We also calculate the
magnetic fields resulting from the higher order HE, TE, and
TM modes and compare them to the fundamental HE mode.Comment: 8 pages, 6 figure
Extended Bose Hubbard model for two leg ladder systems in artificial magnetic fields
We investigate the ground state properties of ultracold atoms with long range
interactions trapped in a two leg ladder configuration in the presence of an
artificial magnetic field. Using a Gross-Pitaevskii approach and a mean field
Gutzwiller variational method, we explore both the weakly interacting and
strongly interacting regime, respectively. We calculate the boundaries between
the density-wave/supersolid and the Mott-insulator/superfluid phases as a
function of magnetic flux and uncover regions of supersolidity. The mean-field
results are confirmed by numerical simulations using a cluster mean field
approach.Comment: 11 pages, 11 figure
Twonniers: Interaction-induced effects on Bose-Hubbard parameters
We study the effects of the repulsive on-site interactions on the broadening
of the localized Wannier functions used for calculating the parameters to
describe ultracold atoms in optical lattices. For this, we replace the common
single-particle Wannier functions, which do not contain any information about
the interactions, by two-particle Wannier functions ("Twonniers") obtained from
an exact solution which takes the interactions into account. We then use these
interaction-dependent basis functions to calculate the Bose--Hubbard model
parameters, showing that they are substantially different both at low and high
lattice depths, from the ones calculated using single-particle Wannier
functions. Our results suggest that density effects are not negligible for many
parameter ranges and need to be taken into account in metrology experiments.Comment: 6 pages, 3 figure
Two-leg ladder Bose Hubbard models with staggered fluxes
We investigate the ground state properties of ultracold atoms trapped in a
two-leg ladder potential in the presence of an artificial magnetic field in a
staggered configuration. We focus on the strongly interacting regime and use
the Landau theory of phase transitions and a mean field Gutzwiller variational
method to identify the stable superfluid phases and their boundaries with the
Mott-insulator regime as a function of magnetic flux. In addition, we calculate
the local and chiral currents of these superfluid phases, which show a
staggered vortex anti-vortex configuration. The analytical results are
confirmed by numerical simulations using a cluster mean-field theory approach.Comment: 9 pages, 7 figure
Density Wave -Supersolid and Mott Insulator-Superfluid transition in presence of an artificial gauge field : a strong coupling perturbation approach
We study the effect of an artificial gauge field on the zero temperature
phase diagram of extended Bose Hubbard model, that describes ultra cold atoms
in optical lattices with long range interaction using strong coupling
perturbation theory . We determine analytically the effect of the artificial
gauge field on the density wave - supersolid (DW-SS) and the the Mott
insulator-superfluid (MI -SF) transition boundary . The momentum distribution
at these two transition boundaries is also calculated in this approach. It is
shown that such momentum distribution which can be observed in time of flight
measurement, reveals the symmetry of the gauge potential through the formation
of magnetic Brillouin zone and clearly distinguishes between the DW-SS and
MI-SF boundary. We also point out that in symmetric gauge the momentum
distribution structure at these transition boundaries bears distinctive
signatures of vortices in supersolid and superfluid phases.Comment: 18 latexed two column pages including appendix, 9 .eps figures Figure
positioning readjusted and one reference adde