45 research outputs found
The Efimov effect for three interacting bosonic dipoles
Three oriented bosonic dipoles are treated using the hyperspherical adiabatic
representation, providing numerical evidence that the Efimov effect persists
near a two-dipole resonance and in a system where angular momentum is not
conserved. Our results further show that the Efimov features in scattering
observables become universal, with a known three-body parameter, i.e. the
resonance energies depend only on the two-body physics, which also has
implications for the universal spectrum of the four-dipole problem. Moreover,
the Efimov states should be long-lived, which is favorable for their creation
and manipulation in ultracold dipolar gases. Finally, deeply-bound two-dipole
states are shown to be relatively stable against collisions with a third
dipole, owing to the emergence of a repulsive interaction originating in the
angular momentum nonconservation for this system.Comment: 4 pages, 2 figures, 1 tabl
Origin of the Three-body Parameter Universality in Efimov Physics
In recent years extensive theoretical and experimental studies of universal
few-body physics have led to advances in our understanding of universal Efimov
physics [1]. The Efimov effect, once considered a mysterious and esoteric
effect, is today a reality that many experiments in ultracold quantum gases
have successfully observed and continued to explore [2-14]. Whereas theory was
the driving force behind our understanding of Efimov physics for decades,
recent experiments have contributed an unexpected discovery. Specifically,
measurements have found that the so-called three-body parameter determining
several properties of the system is universal, even though fundamental
assumptions in the theory of the Efimov effect suggest that it should be a
variable property that depends on the precise details of the short-range two-
and three-body interactions. The present Letter resolves this apparent
contradiction by elucidating unanticipated implications of the two-body
interactions. Our study shows that the three-body parameter universality
emerges because a universal effective barrier in the three-body potentials
prevents the three particles from simultaneously getting close to each other.
Our results also show limitations on this universality, as it is more likely to
occur for neutral atoms and less likely to extend to light nuclei.Comment: 11 pages; 9 figures. Includes Supplementary Materia
Mass Dependence of Ultracold Three-Body Collision Rates
We show that many aspects of ultracold three-body collisions can be
controlled by choosing the mass ratio between the collision partners. In the
ultracold regime, the scattering length dependence of the three-body rates can
be substantially modified from the equal mass results. We demonstrate that the
only non-trivial mass dependence is due solely to Efimov physics. We have
determined the mass dependence of the three-body collision rates for all
heteronuclear systems relevant for two-component atomic gases with resonant
s-wave interspecies interactions, which includes only three-body systems with
two identical bosons or two identical fermions
General Theoretical Description of \u3cem\u3eN\u3c/em\u3e-Body Recombination
Formulas for the cross section and event rate constant describing recombination of N particles are derived in terms of general S-matrix elements. Our result immediately yields the generalized Wigner threshold scaling for the recombination of N bosons. A semianalytical formula encapsulates the overall scaling with energy and scattering length, as well as resonant modifications by the presence of N-body states near the threshold collision energy in the entrance channel. We then apply our model to the case of four-boson recombination into an Efimov trimer and a free atom
Scattering length for helium atom-diatom collision
We present results on the scattering lengths of ^4He--^4He_2 and ^3He--^4He_2
collisions. We also study the consequence of varying the coupling constant of
the atom-atom interaction.Comment: Contribution to Proceedings of the International Workshop ``Critical
Stability of Few-Body Quantum Systems'' (Dresden, October 17--22, 2005