Ultracold three-body collisions near overlapping Feshbach resonances

We present a comprehensive collection of ultracold three-body collisions properties near overlapping Feshbach resonances. Our results incorporate variations of all scattering lengths and demonstrate novel collisional behavior, such as atom-molecule interference effects. Taking advantage of the unique ways in which these collisions reflect Efimov physics, new pathways to control atomic and molecular losses open up. Further, we show that overlapping resonances can greatly improve the chances of observing multiple Efimov features in an ultracold quantum gas for nearly any system.Comment: 4 pages, 3 figures, 1 tabl

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

Three-boson problem near a narrow Feshbach resonance

We consider a three-boson system with resonant binary interactions and show that three-body observables depend only on the resonance width and the scattering length. The effect of narrow resonances is qualitatively different from that of wide resonances revealing novel physics of three-body collisions. We calculate the rate of three-body recombination to a weakly bound level and the atom-dimer scattering length and discuss implications for experiments on Bose-Einstein condensates and atom-molecule mixtures near Feshbach resonances.Comment: published versio

Dimer-atom scattering between two identical fermions and a third particle

We use the diagrammatic $T$-matrix approach to analyze the three-body scattering problem between two identical fermions and a third particle (which could be a different species of fermion or a boson). We calculate the s-wave dimer-atom scattering length for all mass ratios, and our results exactly match the results of Petrov. In particular, we list the exact dimer-atom scattering lengths for all available two-species Fermi-Fermi and Bose-Fermi mixtures. In addition, unlike that of the equal-mass particles case where the three-body scattering $T$-matrix decays monotonically as a function of the outgoing momentum, we show that, after an initial rapid drop, this function changes sign and becomes negative at large momenta and then decays slowly to zero when the mass ratio of the fermions to the third particle is higher than a critical value (around 6.5). As the mass ratio gets higher, modulations of the $T$-matrix become more apparent with multiple sign changes, related to the "fall of a particle to the center" phenomenon and to the emergence of three-body Efimov bound states.Comment: 6 pages, 3 figures, and 2 table

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

The structure of the atomic helium trimers: Halos and Efimov states

The Faddeev equations for the atomic helium-trimer systems are solved numerically with high accuracy both for the most sophisticated realistic potentials available and for simple phenomenological potentials. An efficient numerical procedure is described. The large-distance asymptotic behavior, crucial for weakly bound three-body systems, is described almost analytically for arbitrary potentials. The Efimov effect is especially considered. The geometric structures of the bound states are quantitatively investigated. The accuracy of the schematic models and previous computations is comparable, i.e. within 20% for the spatially extended states and within 40% for the smaller ^4He-trimer ground state.Comment: 32 pages containing 7 figures and 6 table

Ultracold atom-molecule collisions with fermionic atoms

Elastic and inelastic properties of weakly bound s- and p-wave molecules of fermionic atoms that collide with a third atom are investigated. Analysis of calculated collisional properties of s-wave dimers of fermions in different spin states permit us to compare and highlight the physical mechanisms that determine the stability of s-wave and p-wave molecules. In contrast to s-wave molecules, the collisional properties of p-wave molecules are found to be largely insensitive to variations of the p-wave scattering length and that these collisions will usually result in short molecular lifetimes. We also discuss the importance of this result for both theories and experiments involving degenerate Fermi gases.Comment: 6 pages, 2 figure

Range Corrections to Three-Body Observables near a Feshbach Resonance

A non-relativistic system of three identical particles will display a rich set of universal features known as Efimov physics if the scattering length a is much larger than the range l of the underlying two-body interaction. An appropriate effective theory facilitates the derivation of both results in the |a| goes to infinity limit and finite-l/a corrections to observables of interest. Here we use such an effective-theory treatment to consider the impact of corrections linear in the two-body effective range, r_s on the three-boson bound-state spectrum and recombination rate for |a| much greater than |r_s|. We do this by first deriving results appropriate to the strict limit |a| goes to infinity in coordinate space. We then extend these results to finite a using once-subtracted momentum-space integral equations. We also discuss the implications of our results for experiments that probe three-body recombination in Bose-Einstein condensates near a Feshbach resonance.Comment: 28 pages, 3 figure

Adiabatic hyperspherical study of triatomic helium systems

The 4He3 system is studied using the adiabatic hyperspherical representation. We adopt the current state-of-the-art helium interaction potential including retardation and the nonadditive three-body term, to calculate all low-energy properties of the triatomic 4He system. The bound state energies of the 4He trimer are computed as well as the 4He+4He2 elastic scattering cross sections, the three-body recombination and collision induced dissociation rates at finite temperatures. We also treat the system that consists of two 4He and one 3He atoms, and compute the spectrum of the isotopic trimer 4He2 3He, the 3He+4He2 elastic scattering cross sections, the rates for three-body recombination and the collision induced dissociation rate at finite temperatures. The effects of retardation and the nonadditive three-body term are investigated. Retardation is found to be significant in some cases, while the three-body term plays only a minor role for these systems.Comment: 24 pages 6 figures Submitted to Physical Review