68 research outputs found
Periodic spin textures in a degenerate F=1 Rb spinor Bose gas
We report on the spin textures produced by cooling unmagnetized Rb F=1
spinor gases into the regime of quantum degeneracy. At low temperatures,
magnetized textures form that break translational symmetry and display
short-range periodic magnetic order characterized by one- or two-dimensional
spatial modulations with wavelengths much smaller than the extent of the
quasi-two-dimensional degenerate gas. Spin textures produced upon cooling spin
mixtures with a non-zero initial magnetic quadrupole moment also show
ferromagnetic order that, at low temperature, coexists with the spatially
modulated structure.Comment: 6 pages, revised substantially following reviewer comments and
further analysi
Coherence-enhanced imaging of a degenerate Bose gas
We present coherence-enhanced imaging, an in situ technique that uses Raman
superradiance to probe the spatial coherence properties of an ultracold gas.
Applying this method, we obtain a spatially resolved measurement of the
condensate number and more generally, of the first-order spatial correlation
function in a gas of Rb atoms. We observe the enhanced decay of
propagating spin gratings in high density regions of a Bose condensate, a decay
we ascribe to collective, non-linear atom-atom scattering. Further, we directly
observe spatial inhomogeneities that arise generally in the course of extended
sample superradiance.Comment: 4 pages, 4 figure
Spontaneous Vortex Lattices in Quasi 2D Dipolar Spinor Condensates
Motivated by recent experiments\cite{BA}\cite{BB}, we study quasi 2D
ferromagnetic condensates with various aspect ratios. We find that in zero
magnetic field, dipolar energy generates a local energy minimum with all the
spins lie in the 2D plane forming a row of {\em circular} spin textures with
{\em alternating} orientation, corresponding to a packing of vortices of {\em
identical} vorticity in different spin components. In a large magnetic field,
the system can fall into a long lived dynamical state consisting of an array of
elliptic and hyperbolic Mermin-Ho spin textures, while the true equilibrium is
an uniaxial spin density wave with a single wave-vector along the magnetic
field, and a wavelength similar to the characteristic length of the long lived
vortex array state.Comment: 4 pages, 6 figure
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