889 research outputs found
Mean-Field Theory of Feshbach-Resonant Interactions in 85Rb Condensates
Recent Feshbach-resonance experiments with 85Rb Bose-Einstein condensates
have led to a host of unexplained results: dramatic losses of condensate atoms
for an across-resonance sweep of the magnetic field, a collapsing condensate
with a burst of atoms emanating from the remnant condensate, increased losses
for decreasing interaction times-- until short times are reached, and seemingly
coherent oscillations between remnant and burst atoms. Using a simple yet
realistic mean-field model, we find that rogue dissociation, molecular
dissociation to noncondensate atom pairs, is strongly implicated as the
physical mechanism responsible for these observations.Comment: v2: numbers changed, not conclusions; 5 pages, 3 figures, submitted
to PR
Light propagation beyond the mean-field theory of standard optics
With ready access to massive computer clusters we may now study light
propagation in a dense cold atomic gas by means of basically exact numerical
simulations. We report on a direct comparison between traditional optics, that
is, electrodynamics of a polarizable medium, and numerical simulations in an
elementary problem of light propagating through a slab of matter. The standard
optics fails already at quite low atom densities, and the failure becomes
dramatic when the average interatomic separation is reduced to around ,
where is the wave number of resonant light. The difference between the two
solutions originates from correlations between the atoms induced by
light-mediated dipole-dipole interactions
Rate limit for photoassociation of a Bose-Einstein condensate
We simulate numerically the photodissociation of molecules into noncondensate
atom pairs that accompanies photoassociation of an atomic Bose-Einstein
condensate into a molecular condensate. Such rogue photodissociation sets a
limit on the achievable rate of photoassociation. Given the atom density \rho
and mass m, the limit is approximately 6\hbar\rho^{2/3}/m. At low temperatures
this is a more stringent restriction than the unitary limit of scattering
theory.Comment: 5 pgs, 18 refs., 3 figs., submitted to Phys. Rev. Let
Comment on "Stimulated Raman adiabatic passage from an atomic to a molecular Bose-Einstein condensate"
Collective two-color photoassociation of a freely-interacting 87Rb
Bose-Einstein condensate is theoretically examined, focusing on stimulated
Raman adiabatic passage (STIRAP) from an atomic to a stable molecular
condensate. In particular, Drummond et al. [Phys. Rev. A 65, 063619 (2002);
cond-mat/0110578] have predicted that particle-particle interactions can limit
the efficiency of collective atom-molecule STIRAP, and that optimizing the
laser parameters can partially overcome this limitation. We suggest that the
molecular conversion efficiency can be further improved by treating the initial
condensate density as an optimization parameter.Comment: 2 pages, 1 figure, re-submitted to PRA; v4 is our final answer;
removed results on Feshbach-tuned efficiency; added discussion of negligible
noncondensate mode
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