1,335 research outputs found
Vortex formation in a stirred Bose-Einstein condensate
Using a focused laser beam we stir a Bose-Einstein condensate of 87Rb
confined in a magnetic trap and observe the formation of a vortex for a
stirring frequency exceeding a critical value. At larger rotation frequencies
we produce states of the condensate for which up to four vortices are
simultaneously present. We have also measured the lifetime of the single vortex
state after turning off the stirring laser beam.Comment: 4 pages, 3 figure
An Atom Faucet
We have constructed and modeled a simple and efficient source of slow atoms.
From a background vapour loaded magneto-optical trap, a thin laser beam
extracts a continuous jet of cold rubidium atoms. In this setup, the extraction
column that is typical to leaking MOT systems is created without any optical
parts placed inside the vacuum chamber. For detailed analysis, we present a
simple 3D numerical simulation of the atomic motion in the presence of multiple
saturating laser fields combined with an inhomogeneous magnetic field. At a
pressure of mbar, the moderate laser power of
10 mW per beam generates a jet of flux atoms/s with a
mean velocity of 14 m/s and a divergence of mrad.Comment: Submitted to EPJD. 1 TeX file (EPJ format), 7 picture
Bose-Einstein Condensates with Large Number of Vortices
We show that as the number of vortices in a three dimensional Bose-Einstein
Condensate increases, the system reaches a "quantum Hall" regime where the
density profile is a Gaussian in the xy-plane and an inverted parabolic profile
along z. The angular momentum of the system increases as the vortex lattice
shrinks. However, Coriolis force prevents the unit cell of the vortex lattice
from shrinking beyond a minimum size. Although the recent MIT experiment is not
exactly in the quantum Hall regime, it is close enough for the present results
to be used as a guide. The quantum Hall regime can be easily reached by
moderate changes of the current experimental parameters.Comment: 4 pages, no figure
Interferometric detection of a single vortex in a dilute Bose-Einstein condensate
Using two radio frequency pulses separated in time we perform an amplitude
division interference experiment on a rubidium Bose-Einstein condensate. The
presence of a quantized vortex, which is nucleated by stirring the condensate
with a laser beam, is revealed by a dislocation in the fringe pattern.Comment: 4 pages, 4 figure
Dissipative dynamics of vortex arrays in trapped Bose-condensed gases: neutron stars physics on K scale
We develop a theory of dissipative dynamics of large vortex arrays in trapped
Bose-condensed gases. We show that in a static trap the interaction of the
vortex array with thermal excitations leads to a non-exponential decay of the
vortex structure, and the characteristic lifetime depends on the initial
density of vortices. Drawing an analogy with physics of pulsar glitches, we
propose an experiment which employs the heating of the thermal cloud in the
course of the decay of the vortex array as a tool for a non-destructive study
of the vortex dynamics.Comment: 4 pages, revtex; revised versio
Nonlinear interference in a mean-field quantum model
Using similar nonlinear stationary mean-field models for Bose-Einstein
Condensation of cold atoms and interacting electrons in a Quantum Dot, we
propose to describe the original many-particle ground state as a one-particle
statistical mixed state of the nonlinear eigenstates whose weights are provided
by the eigenstate non-orthogonality. We search for physical grounds in the
interpretation of our two main results, namely, quantum-classical nonlinear
transition and interference between nonlinear eigenstates.Comment: RevTeX (pdfLaTeX), 7 pages with 5 png-figures include
Dynamic instability of a rotating Bose-Einstein condensate
We consider a Bose-Einstein condensate subject to a rotating harmonic
potential, in connection with recent experiments leading to the formation of
vortices. We use the classical hydrodynamic approximation to the non-linear
Schr\"odinger equation to determine almost analytically the evolution of the
condensate. We predict that this evolution can exhibit dynamical instabilities,
for the stirring procedure previously demonstrated at ENS and for a new
stirring procedure that we put forward. These instabilities take place within
the range of stirring frequency and amplitude for which vortices are produced
experimentally. They provide therefore an initiating mechanism for vortex
nucleation.Comment: 4 pages, 3 figures, last version including comparison with
experiment
Vortex lattices in a stirred Bose-Einstein condensate
We stir with a focused laser beam a Bose-Einstein condensate of Rb
atoms confined in a magnetic trap. We observe the formation of a single vortex
for a stirring frequency exceeding a critical value. At larger rotation
frequencies we produce states of the condensate for which up to eleven vortices
are simultaneously present. We present measurements of the decay of a vortex
array once the stirring laser beam is removed
Vortex lattice formation in a rotating Bose-Einstein condensate
We study the dynamics of vortex lattice formation of a rotating trapped
Bose-Einstein condensate by numerically solving the two-dimensional
Gross-Pitaevskii equation, and find that the condensate undergoes elliptic
deformation, followed by unstable surface-mode excitations before forming a
quantized vortex lattice. The origin of the peculiar surface-mode excitations
is identified to be phase fluctuations at the low-density surface regime. The
obtained dependence of a distortion parameter on time and that on the driving
frequency agree with the recent experiments by Madison {\it et al.} [Phys. Rev.
Lett. {\bf 86}, 4443 (2001)].Comment: 4 pages, 4 figure
Kelvin Modes of a fast rotating Bose-Einstein Condensate
Using the concept of diffused vorticity and the formalism of rotational
hydrodynamics we calculate the eigenmodes of a harmonically trapped
Bose-Einstein condensate containing an array of quantized vortices. We predict
the occurrence of a new branch of anomalous excitations, analogous to the
Kelvin modes of the single vortex dynamics. Special attention is devoted to the
excitation of the anomalous scissors mode.Comment: 7 pages, 3 figures, submitted to Phys. Rev.
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