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.

Figure 1

Idealized picture for two overlapping $s$-wave Feshbach resonances between $B$ and $X$ atomic species, focusing on just one of the resonances. In (a) there are one or two weakly bound molecular states, and in (b) zero or one molecular state can exist. The regions (I)–(IV) in each case exhaust all scenarios in general.

Figure 2

Effect of overlapping resonances on (a) the strength of the Efimov potential $s_0$ [see Eq. (1)] and (b) the scale factor $e^{\pi /s_0}$ separating Efimov features as a function of $a$. Both panels include the results for large scattering lengths between two ($s_0$, green dashed line) and three ($s_0^{*}$, red solid line) pairs of particles.

Figure 3

The magnetic field dependence of selected processes using the present results. Reactive scattering showing (a) interference minima and (b) both interference minima and resonant enhancement. (c) Atom-molecule collision rates for three-spin mixtures of ${}^6\mathrm{Li}$ [4] for the region in (d) where all three scattering lengths are large and positive.