The universality of the Efimov three-body parameter
  In this paper we discuss the recent discovery of the universality of the three-body parameter (3BP) from Efimov physics. This new result was identified by recent experimental observations in ultracold quantum gases where the value of the s-wave scattering length, $a=a_-$, at which the first Efimov resonance is created was found to be nearly the same for a range of atomic species --- if scaled as $a_-/r_{\rm vdW}$, where $r_{\rm vdW}$ is the van der Waals length. Here, we discuss some of the physical principles related to these observations that emerge from solving the three-body problem with van der Waals interactions in the hyperspherical formalism. We also demonstrate the strong three-body multichannel nature of the problem and the importance of properly accounting for nonadiabatic effects. 
J. P. D'Incao, J. Wang, B. D. Esry, and C. H. Greene
cond-mat.quant-gas physics.atom-ph quant-ph