482 research outputs found
Boojums in Rotating Two-Component Bose-Einstein Condensates
A boojum is a topological defect that can form only on the surface of an
ordered medium such as superfluid He and liquid crystals. We study
theoretically boojums appearing between two phases with different vortex
structures in two-component BECs where the intracomponent interaction is
repulsive in one phase and attractive in the other. The detailed structure of
the boojums is revealed by investigating its density distribution, effective
superflow vorticity and pseudospin texture.Comment: 4 pages, 4 figure
Vortex sheet in rotating two-component Bose-Einstein condensates
We investigate vortex states of immiscible two-component Bose-Einstein
condensates under rotation through numerical simulations of the coupled
Gross-Pitaevskii equations. For strong intercomponent repulsion, the two
components undergo phase separation to form several density domains of the same
component. In the presence of the rotation, the nucleated vortices are aligned
between the domains to make up winding chains of singly quantized vortices, a
vortex sheet, instead of periodic vortex lattices. The vortices of one
component are located at the region of the density domains of the other
component, which results in the serpentine domain structure. The sheet
configuration is stable as long as the imbalance of the intracomponent
parameter is small. We employ a planar sheet model to estimate the distance
between neighboring sheets, determined by the competition between the surface
tension of the domain wall and the kinetic energy of the superflow via
quantized vortices. By comparing the several length scales in this system, the
phase diagram of the vortex state is obtained.Comment: 8 pages, 7 figure
Disorderless quasi-localization of polar gases in one-dimensional lattices
One-dimensional polar gases in deep optical lattices present a severely
constrained dynamics due to the interplay between dipolar interactions, energy
conservation, and finite bandwidth. The appearance of dynamically-bound
nearest-neighbor dimers enhances the role of the dipolar tail,
resulting, in the absence of external disorder, in quasi-localization via dimer
clustering for very low densities and moderate dipole strengths. Furthermore,
even weak dipoles allow for the formation of self-bound superfluid lattice
droplets with a finite doping of mobile, but confined, holons. Our results,
which can be extrapolated to other power-law interactions, are directly
relevant for current and future lattice experiments with magnetic atoms and
polar molecules.Comment: 5 + 2 Page
Vortex Lattice Structures of a Bose-Einstein Condensate in a Rotating Lattice Potential
We study vortex lattice structures of a trapped Bose-Einstein condensate in a
rotating lattice potential by numerically solving the time-dependent
Gross-Pitaevskii equation. By rotating the lattice potential, we observe the
transition from the Abrikosov vortex lattice to the pinned lattice. We
investigate the transition of the vortex lattice structure by changing
conditions such as angular velocity, intensity, and lattice constant of the
rotating lattice potential.Comment: 6 pages, 8 figures, submitted to Quantum Fluids and Solids Conference
(QFS 2006
Vortex phase diagram in rotating two-component Bose-Einstein condensates
We investigate the structure of vortex states in rotating two-component
Bose-Einstein condensates with equal intracomponent but varying intercomponent
coupling constants. A phase diagram in the intercomponent-coupling versus
rotation-frequency plane reveals rich equilibrium structures of vortex states.
As the ratio of intercomponent to intracomponent couplings increases, the
interlocked vortex lattices undergo phase transitions from triangular to
square, to double-core lattices, and eventually develop interwoven "serpentine"
vortex sheets with each component made up of chains of singly quantized
vortices.Comment: 4 pages, 4 figures, revtex
Non classical velocity statistics in a turbulent atomic Bose Einstein condensate
In a recent experiment Paoletti et al (Phys. Rev. Lett. 101, 154501, 2008)
monitored the motion of tracer particles in turbulent superfluid helium and
inferred that the velocity components do not obey the Gaussian statistics
observed in ordinary turbulence. Motivated by their experiment, we create a
small turbulent state in an atomic Bose-Einstein condensate, which enables us
to compute directly the velocity field, and we find similar non-classical
power-law tails. Our result thus suggests that non-Gaussian turbulent velocity
statistics describe a fundamental property of quantum fluids. We also track the
decay of the vortex tangle in the presence of the thermal cloud.Comment: 10 pages, 3 figure
Quantum Kelvin-Helmholtz instability in phase-separated two-component Bose-Einstein condensates
We theoretically study the Kelvin-Helmholtz instability in phase-separated
two-component Bose-Einstein condensates using the Gross-Pitaevskii and
Bogoliubov-de Gennes models. A flat interface between the two condensates is
shown to deform into sawtooth or Stokes-like waves, leading to the formation of
singly quantized vortices on the peaks and troughs of the waves. This scenario
of interface instability in quantum fluids is quite different from that in
classical fluids.Comment: 5 pages, 4 figure
Disorderless Quasi-localization of Polar Gases in One-Dimensional Lattices
One-dimensional polar gases in deep optical lattices present a severely constrained dynamics due to the interplay between dipolar interactions, energy conservation, and finite bandwidth. The appearance of dynamically bound nearest-neighbor dimers enhances the role of the 1/r3 dipolar tail, resulting in the absence of external disorder, in quasi-localization via dimer clustering for very low densities and moderate dipole strengths. Furthermore, even weak dipoles allow for the formation of self-bound superfluid lattice droplets with a finite doping of mobile, but confined, holons. Our results, which can be extrapolated to other power-law interactions, are directly relevant for current and future lattice experiments with magnetic atoms and polar molecules
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