741 research outputs found
Topological Excitations in Spinor Bose-Einstein Condensates
We investigate the properties of skyrmion in the ferromagnetic state of
spin-1 Bose-Einstein condensates by means of the mean-field theory and show
that the size of skyrmion is fixed to the order of the healing length. It is
shown that the interaction between two skyrmions with oppositely rotating spin
textures is attractive when their separation is large, following a unique
power-law behavior with a power of -7/2.Comment: 4 pages, 5 figure
A novel method to create a vortex in a Bose-Einstein condensate
It has been shown that a vortex in a BEC with spin degrees of freedom can be
created by manipulating with external magnetic fields. In the previous work, an
optical plug along the vortex axis has been introduced to avoid Majorana flips,
which take place when the external magnetic field vanishes along the vortex
axis while it is created. In the present work, in contrast, we study the same
scenario without introducing the optical plug. The magnetic field vanishes only
in the center of the vortex at a certain moment of the evolution and hence we
expect that the system will lose only a fraction of the atoms by Majorana flips
even in the absence of an optical plug. Our conjecture is justified by
numerically solving the Gross-Pitaevskii equation, where the full spinor
degrees of freedom of the order parameter are properly taken into account. A
significant simplification of the experimental realization of the scenario is
attained by the omission of the optical plug.Comment: 8 pages, 11 figure
Spin textures in slowly rotating Bose-Einstein Condensates
Slowly rotating spin-1 Bose-Einstein condensates are studied through a
variational approach based upon lowest Landau level calculus. The author finds
that in a gas with ferromagnetic interactions, such as Rb, angular
momentum is predominantly carried by clusters of two different types of
skyrmion textures in the spin-vector order parameter. Conversely, in a gas with
antiferromagnetic interactions, such as Na, angular momentum is carried
by -disclinations in the nematic order parameter which arises from spin
fluctuations. For experimentally relevant parameters, the cores of these
-disclinations are ferromagnetic, and can be imaged with polarized light.Comment: 14 pages, 12 low resolution bitmapped figures, RevTeX4. High
resolution figures available from author. Suplementary movies available from
autho
Magnetization plateaus for spin-one bosons in optical lattices: Stern-Gerlach experiments with strongly correlated atoms
We consider insulating states of spin-one bosons in optical lattices in the
presence of a weak magnetic field. For the states with more than one atom per
lattice site we find a series of quantum phase transitions between states with
fixed magnetization and a canted nematic phase. In the presence of a global
confining potential, this unusual phase diagram leads to several novel
phenomena, including formation of magnetization plateaus. We discuss how these
effects can be observed using spatially resolved density measurements.Comment: 4 pages 5 figure
Polarization of interacting bosons with spin
We demonstrate rigorously that in the absence of explicit spin-dependent
forces one of the ground states of interacting bosons with spin is always fully
polarized -- however complicated the many-body interaction potential might be.
Depending on the particle spin, the polarized ground state will generally be
degenerate with other states, but one can specify the exact degeneracy. For T>0
the magnetization and susceptibility necessarily exceed that of a pure
paramagnet. These results are relevant to recent experiments exploring the
relation between triplet superconductivity and ferromagnetism, and the
Bose-Einstein condensation of atoms with spin. They eliminate the possibility,
raised in some theoretical speculations, that the ground state or positive
temperature state might be antiferromagnetic.Comment: v4: as published in PR
Exact Analysis of Soliton Dynamics in Spinor Bose-Einstein Condensates
We propose an integrable model of a multicomponent spinor Bose-Einstein
condensate in one dimension, which allows an exact description of the dynamics
of bright solitons with spin degrees of freedom. We consider specifically an
atomic condensate in the F=1 hyperfine state confined by an optical dipole
trap. When the mean-field interaction is attractive (c_0 < 0) and the
spin-exchange interaction of a spinor condensate is ferromagnetic (c_2 < 0), we
prove that the system possesses a completely integrable point leading to the
existence of multiple bright solitons. By applying results from the inverse
scattering method, we analyze a collision law for two-soliton solutions and
find that the dynamics can be explained in terms of the spin precession.Comment: 4 pages, 2 figure
Collective Oscillations of Vortex Lattices in Rotating Bose-Einstein Condensates
The complete low-energy collective-excitation spectrum of vortex lattices is
discussed for rotating Bose-Einstein condensates (BEC) by solving the
Bogoliubov-de Gennes (BdG) equation, yielding, e.g., the Tkachenko mode
recently observed at JILA. The totally symmetric subset of these modes includes
the transverse shear, common longitudinal, and differential longitudinal modes.
We also solve the time-dependent Gross-Pitaevskii (TDGP) equation to simulate
the actual JILA experiment, obtaining the Tkachenko mode and identifying a pair
of breathing modes. Combining both the BdG and TDGP approaches allows one to
unambiguously identify every observed mode.Comment: 5 pages, 4 figure
Ultra-Low-Temperature Growth of High-Integrity Gate Oxide Films by Low-Energy Ion-Assisted Oxidation
Magnetic Soliton and Soliton Collisions of Spinor Bose-Einstein Condensates in an Optical Lattice
We study the magnetic soliton dynamics of spinor Bose-Einstein condensates in
an optical lattice which results in an effective Hamiltonian of anisotropic
pseudospin chain. A modified Landau-Lifshitz equation is derived and exact
magnetic soliton solutions are obtained analytically. Our results show that the
time-oscillation of the soliton size can be controlled in practical experiment
by adjusting of the light-induced dipole-dipole interaction. Moreover, the
elastic collision of two solitons is investigated.Comment: 16 pages, 5 figure
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