372 research outputs found
Collisional Aspects of Bosonic and Fermionic Dipoles in Quasi-Two-Dimensional Confining Geometries
Fundamental aspects of ultracold collisions between identical bosonic or
fermionic dipoles are studied under quasi-two-dimensional (Q2D) confinement. In
the strongly dipolar regime, bosonic and fermion species are found to share
important collisional properties as a result of the confining geometry, which
suppresses the inelastic rates irrespective of the quantum statistics obeyed. A
potential negative is that the confinement causes dipole-dipole resonances to
be extremely narrow, which could make it difficult to explore Q2D dipolar gases
with tunable interactions. Such properties are shown to be universal, and a
simple WKB model reproduces most of our numerical results. In order to shed
light on the many-body behavior of dipolar gases in Q2D we have analyzed the
scattering amplitude and developed an energy-analytic form of the
pseudopotentials for dipoles. For specific values of the dipolar interaction,
the pseudopotential coefficient can be tuned to arbitrarily large values,
indicating the possibility of realizing Q2D dipolar gases with tunable
interactions.Comment: 4.1 pages, 3 figure
Suppression of molecular decay in ultracold gases without Fermi statistics
We study inelastic processes for ultracold three-body systems in which only
one interaction is resonant. We have found that the decay rates for weakly
bound molecules due to collisions with other atoms can be suppressed not only
without fermionic statistics but also when bosonic statistics applies. In
addition, we show that at ultracold temperatures three-body recombination
involving a single resonant pair of atoms leads mainly to formation of weakly
bound molecules which, in turn, are stable against decay. These results
indicate that recombination in three-component atomic gases can be used as an
efficient mechanism for molecular formation, allowing the achievement of high
molecular densities
Universality in Three- and Four-Body Bound States of Ultracold Atoms
Under certain circumstances, three or more interacting particles may form
bound states. While the general few-body problem is not analytically solvable,
the so-called Efimov trimers appear for a system of three particles with
resonant two-body interactions. The binding energies of these trimers are
predicted to be universally connected to each other, independent of the
microscopic details of the interaction. By exploiting a Feshbach resonance to
widely tune the interactions between trapped ultracold lithium atoms, we find
evidence for two universally connected Efimov trimers and their associated
four-body bound states. A total of eleven precisely determined three- and
four-body features are found in the inelastic loss spectrum. Their relative
locations on either side of the resonance agree well with universal theory,
while a systematic deviation from universality is found when comparing features
across the resonance.Comment: 16 pages including figures and Supplementary Online Materia
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