3,829 research outputs found
Observation of Topologically Stable 2D Skyrmions in an Antiferromagnetic Spinor Bose-Einstein Condensate
We present the creation and time evolution of two-dimensional Skyrmion
excitations in an antiferromagnetic spinor Bose-Einstein condensate. Using a
spin rotation method, the Skyrmion spin textures were imprinted on a sodium
condensate in a polar phase, where the two-dimensional Skyrmion is
topologically protected. The Skyrmion was observed to be stable on a short time
scale of a few tens of ms but to have dynamical instability to deform its shape
and eventually decay to a uniform spin texture. The deformed spin textures
reveal that the decay dynamics involves breaking the polar phase inside the
condensate without having topological charge density flow through the boundary
of the finite-sized sample. We discuss the possible formation of half-quantum
vortices in the deformation process.Comment: 5 pages, 5 figure
Relaxation of superfluid turbulence in highly oblate Bose-Einstein condensates
We investigate thermal relaxation of superfluid turbulence in a highly oblate
Bose-Einstein condensate. We generate turbulent flow in the condensate by
sweeping the center region of the condensate with a repulsive optical
potential. The turbulent condensate shows a spatially disordered distribution
of quantized vortices and the vortex number of the condensate exhibits
nonexponential decay behavior which we attribute to the vortex pair
annihilation. The vortex-antivortex collisions in the condensate are identified
with crescent-shaped, coalesced vortex cores. We observe that the
nonexponential decay of the vortex number is quantitatively well described by a
rate equation consisting of one-body and two-body decay terms. In our
measurement, we find that the local two-body decay rate is closely proportional
to , where is the temperature and is the chemical potential.Comment: 7 pages, 9 figure
Observation of a Geometric Hall Effect in a Spinor Bose-Einstein Condensate with a Skyrmion Spin Texture
For a spin-carrying particle moving in a spatially varying magnetic field,
effective electromagnetic forces can arise due to the geometric phase
associated with adiabatic spin rotation of the particle. We report the
observation of a geometric Hall effect in a spinor Bose-Einstein condensate
with a skyrmion spin texture. Under translational oscillations of the spin
texture, the condensate resonantly develops a circular motion in a harmonic
trap, demonstrating the existence of an effective Lorentz force. When the
condensate circulates, quantized vortices are nucleated in the boundary region
of the condensate and the vortex number increases over 100 without significant
heating. We attribute the vortex nucleation to the shearing effect of the
effective Lorentz force from the inhomogeneous effective magnetic field.Comment: 9 pages, 11 figure
Emission of Spin-correlated Matter-wave Jets from Spinor Bose-Einstein Condensates
We report the observation of matter-wave jet emission in a strongly
ferromagnetic spinor Bose-Einstein condensate of Li atoms. Directional
atomic beams with and spin states
are generated from state condensates, or vice versa. This
results from collective spin-mixing scattering events, where spontaneously
produced pairs of atoms with opposite momentum facilitates additional
spin-mixing collisions as they pass through the condensates. The matter-wave
jets of different spin states () can be a macroscopic
Einstein-Podolsky-Rosen state with spacelike separation. Its spin-momentum
correlations are studied by using the angular correlation function for each
spin state. Rotating the spin axis, the inter-spin and intra-spin momentum
correlation peaks display a high contrast oscillation, indicating collective
coherence of the atomic ensembles. We provide numerical calculations that
describe the experimental results at a quantitative level and can identify its
entanglement after 100~ms of a long time-of-flight.Comment: 13 pages(6 main text, 7 supplemental material), 12 figure
Coherent many-body spin dynamics in a long-range interacting Ising chain
Coherent many-body quantum dynamics lies at the heart of quantum simulation
and quantum computation. Both require coherent evolution in the exponentially
large Hilbert space of an interacting many-body system. To date, trapped ions
have defined the state of the art in terms of achievable coherence times in
interacting spin chains. Here, we establish an alternative platform by
reporting on the observation of coherent, fully interaction-driven quantum
revivals of the magnetization in Rydberg-dressed Ising spin chains of atoms
trapped in an optical lattice. We identify partial many-body revivals at up to
about ten times the characteristic time scale set by the interactions. At the
same time, single-site-resolved correlation measurements link the magnetization
dynamics with inter-spin correlations appearing at different distances during
the evolution. These results mark an enabling step towards the implementation
of Rydberg atom based quantum annealers, quantum simulations of higher
dimensional complex magnetic Hamiltonians, and itinerant long-range interacting
quantum matter.Comment: 11 pages, 9 figure
- …