441 research outputs found
Dynamics of rotating Bose-Einstein condensates probed by Bragg scattering
Gaseous Bose-Einstein condensates (BECs) have become an important test bed
for studying the dynamics of quantized vortices. In this work we use two-photon
Doppler sensitive Bragg scattering to study the rotation of sodium BECs. We
analyze the microscopic flow field and present laboratory measurements of the
coarse-grained velocity profile. Unlike time-of-flight imaging, Bragg
scattering is sensitive to the direction of rotation and therefore to the phase
of the condensate. In addition, we have non-destructively probed the vortex
flow field using a sequence of two Bragg pulses.Comment: 13 pages, 5 figures. Invited paper submitted to a special issue on
"Nonlinear Waves" of the (Elsevier) journal 'Math. Comput. Simul.', for
participants in the 4th IMACS International Conference on Nonlinear Evolution
Equations and Wave Phenomena (2005). Visit our website at
http://www.physics.gatech.edu/chandra for additional informatio
Bragg Spectroscopy of Vortex Lattices in Bose-Einstein condensates
We have measured the velocity field of a vortex lattice within a sodium
Bose-Einstein condensate using Bragg scattering. The phase gradient of the
macroscopic wavefunction was mapped into the spatial structure of the
diffracted atom cloud, allowing for single shot measurement of the rotation
parameters. A combination of spectral and spatial information yields a complete
description of the superfluid flow, coarse-grained over the lattice structure,
including direct and independent measurements of the rate and sense of
rotation. Signatures of the microscopic quantum rotation have also been
observed.Comment: 5 pages, 5 Figures, A movie built from the CM data is available in
our Webpage: http://www.physics.gatech.edu/chandra/index.htm; added Fig.5
presents new data, showing signatures of the microscopic vortex structure in
the diffracted clou
Spinor condensates and light scattering from Bose-Einstein condensates
These notes discuss two aspects of the physics of atomic Bose-Einstein
condensates: optical properties and spinor condensates. The first topic
includes light scattering experiments which probe the excitations of a
condensate in both the free-particle and phonon regime. At higher light
intensity, a new form of superradiance and phase-coherent matter wave
amplification were observed. We also discuss properties of spinor condensates
and describe studies of ground--state spin domain structures and dynamical
studies which revealed metastable excited states and quantum tunneling.Comment: 58 pages, 33 figures, to appear in Proceedings of Les Houches 1999
Summer School, Session LXXI
Atom Interferometers
Interference with atomic and molecular matter waves is a rich branch of
atomic physics and quantum optics. It started with atom diffraction from
crystal surfaces and the separated oscillatory fields technique used in atomic
clocks. Atom interferometry is now reaching maturity as a powerful art with
many applications in modern science. In this review we first describe the basic
tools for coherent atom optics including diffraction by nanostructures and
laser light, three-grating interferometers, and double wells on AtomChips. Then
we review scientific advances in a broad range of fields that have resulted
from the application of atom interferometers. These are grouped in three
categories: (1) fundamental quantum science, (2) precision metrology and (3)
atomic and molecular physics. Although some experiments with Bose Einstein
condensates are included, the focus of the review is on linear matter wave
optics, i.e. phenomena where each single atom interferes with itself.Comment: submitted to Reviews of Modern Physic
Seeing spin dynamics in atomic gases
The dynamics of internal spin, electronic orbital, and nuclear motion states
of atoms and molecules have preoccupied the atomic and molecular physics
community for decades. Increasingly, such dynamics are being examined within
many-body systems composed of atomic and molecular gases. Our findings
sometimes bear close relation to phenomena observed in condensed-matter
systems, while on other occasions they represent truly new areas of
investigation. I discuss several examples of spin dynamics that occur within
spinor Bose-Einstein gases, highlighting the advantages of spin-sensitive
imaging for understanding and utilizing such dynamics.Comment: Chapter in upcoming Review Volume entitled "From Atomic to Mesoscale:
The Role of Quantum Coherence in Systems of Various Complexities" from World
Scientifi
Making, probing and understanding Bose-Einstein condensates
Contribution to the proceedings of the 1998 Enrico Fermi summer school on
Bose-Einstein condensation in Varenna, Italy.Comment: Long review paper with ~90 pages, ~20 figures. 2 GIF figures in
separate files (4/5/99 fixed figure
Vortex signatures in annular Bose-Einstein condensates
We consider a Bose-Einstein condensate confined in a ``Mexican hat''
potential, with a quartic minus quadratic radial dependence. We find conditions
under which the ground state is annular in shape, with a hole in the center of
the condensate. Rotation leads to the appearance of stable multiply-quantized
vortices, giving rise to a superfluid flow around the ring. The collective
modes of the system are explored both numerically and analytically using the
Gross-Pitaevskii and hydrodynamic equations. Potential experimental schemes to
detect vorticity are proposed and evaluated, which include measuring the
splitting of collective mode frequencies, observing expansion following release
from the trap, and probing the momentum distribution of the condensate.Comment: 11 pages, 7 figure
Equatorial Waves in Rotating Bubble-Trapped Superfluids
As the Earth rotates, the Coriolis force causes several oceanic and
atmospheric waves to be trapped along the equator, including Kelvin, Yanai,
Rossby, and Poincar\'e modes. It has been demonstrated that the mathematical
origin of these waves is related to the nontrivial topology of the underlying
hydrodynamic equations. Inspired by recent observations of Bose-Einstein
condensation (BEC) in bubble-shaped traps in microgravity ultracold quantum gas
experiments, we show that equatorial modes are supported by a rapidly rotating
condensate in a spherical geometry. Based on a zero-temperature coarse-grained
hydrodynamic framework, we reformulate the coupled oscillations of the
superfluid and the Abrikosov vortex lattice resulting from rotation by a
Schr\"odinger-like eigenvalue problem. The obtained non-Hermitian Hamiltonian
is topologically nontrivial. Furthermore, we solve the hydrodynamic equations
for a spherical geometry and find that the rotating superfluid hosts Kelvin,
Yanai, and Poincar\'e equatorial modes, but not the Rossby mode. Our
predictions can be tested with state-of-the-art bubble-shaped trapped BEC
experiments.Comment: 11 pages, 5 figure
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