7,762 research outputs found
Collapse and Bose-Einstein condensation in a trapped Bose-gas with negative scattering length
We find that the key features of the evolution and collapse of a trapped Bose
condensate with negative scattering length are predetermined by the particle
flux from the above-condensate cloud to the condensate and by 3-body
recombination of Bose-condensed atoms. The collapse, starting once the number
of Bose-condensed atoms reaches the critical value, ceases and turns to
expansion when the density of the collapsing cloud becomes so high that the
recombination losses dominate over attractive interparticle interaction. As a
result, we obtain a sequence of collapses, each of them followed by dynamic
oscillations of the condensate. In every collapse the 3-body recombination
burns only a part of the condensate, and the number of Bose-condensed atoms
always remains finite. However, it can comparatively slowly decrease after the
collapse, due to the transfer of the condensate particles to the
above-condensate cloud in the course of damping of the condensate oscillations.Comment: 11 pages, 3 figure
Finite temperature correlations and density profiles of an inhomogeneous interacting 1D Bose gas
We calculate the density profiles and density correlation functions of the
one-dimensional Bose gas in a harmonic trap, using the exact finite-temperature
solutions for the uniform case, and applying a local density approximation. The
results are valid for a trapping potential which is slowly varying relative to
a correlation length. They allow a direct experimental test of the transition
from the weak coupling Gross-Pitaevskii regime to the strong coupling,
'fermionic' Tonks-Girardeau regime. We also calculate the average two-particle
correlation which characterizes the bulk properties of the sample, and find
that it can be well approximated by the value of the local pair correlation in
the trap center.Comment: Final published version; updated references; 19 pages, 12 figure
Critical Dynamics of a Two-dimensional Superfluid near a Non-Thermal Fixed Point
Critical dynamics of an ultracold Bose gas far from equilibrium is studied in
two spatial dimensions. Superfluid turbulence is created by quenching the
equilibrium state close to zero temperature. Instead of immediately
re-thermalizing, the system approaches a meta-stable transient state,
characterized as a non-thermal fixed point. A focus is set on the vortex
density and vortex-antivortex correlations which characterize the evolution
towards the non-thermal fixed point and the departure to final
(quasi-)condensation. Two distinct power-law regimes in the vortex-density
decay are found and discussed in terms of a vortex binding-unbinding transition
and a kinetic description of vortex scattering. A possible relation to decaying
turbulence in classical fluids is pointed out. By comparing the results to
equilibrium studies of a two-dimensional Bose gas, an intuitive understanding
of the location of the non-thermal fixed point in a reduced phase space is
developed.Comment: 11 pages, 13 figures; PRA versio
Expectation Values in the Lieb-Liniger Bose Gas
Taking advantage of an exact mapping between a relativistic integrable model
and the Lieb-Liniger model we present a novel method to compute expectation
values in the Lieb-Liniger Bose gas both at zero and finite temperature. These
quantities, relevant in the physics of one-dimensional ultracold Bose gases,
are expressed by a series that has a remarkable behavior of convergence. Among
other results, we show the computation of the three-body expectation value at
finite temperature, a quantity that rules the recombination rate of the Bose
gas.Comment: Published version. Selected for the December 2009 issue of Virtual
Journal of Atomic Quantum Fluid
Exact Results for Three-Body Correlations in a Degenerate One-Dimensional Bose Gas
Motivated by recent experiments we derive an exact expression for the
correlation function entering the three-body recombination rate for a
one-dimensional gas of interacting bosons. The answer, given in terms of two
thermodynamic parameters of the Lieb-Liniger model, is valid for all values of
the dimensionless coupling and contains the previously known results
for the Bogoliubov and Tonks-Girardeau regimes as limiting cases. We also
investigate finite-size effects by calculating the correlation function for
small systems of 3, 4, 5 and 6 particles.Comment: 4 pages, 2 figure
Evolution of a Bose-condensed gas under variations of the confining potential
We discuss the dynamic properties of a trapped Bose-condensed gas under
variations of the confining field and find analytical scaling solutions for the
evolving coherent state (condensate). We further discuss the characteristic
features and the depletion of this coherent state.Comment: 4 pages, no postscript figure
Three fully polarized fermions close to a p-wave Feshbach resonance
We study the three-body problem for three atomic fermions, in the same spin
state, experiencing a resonant interaction in the p-wave channel via a Feshbach
resonance represented by a two-channel model. The rate of inelastic processes
due to recombination to deeply bound dimers is then estimated from the
three-body solution using a simple prescription. We obtain numerical and
analytical predictions for most of the experimentally relevant quantities that
can be extracted from the three-body solution: the existence of weakly bound
trimers and their lifetime, the low-energy elastic and inelastic scattering
properties of an atom on a weakly bound dimer (including the atom-dimer
scattering length and scattering volume), and the recombination rates for three
colliding atoms towards weakly bound and deeply bound dimers. The effect of
"background" non-resonant interactions in the open channel of the two-channel
model is also calculated and allows to determine which three-body quantities
are `universal' and which on the contrary depend on the details of the model.Comment: 31 pages, 12 figure
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