Generalized Efimov scenario for heavy-light mixtures.

Motivated by recent experimental investigations of Cs-Cs-Li Efimov resonances, this work theoretically investigates the few-body properties of N-1 noninteracting identical heavy bosons, which interact with a light impurity through a large s-wave scattering length. For Cs-Cs-Cs-Li, we predict the existence of universal four-body states with energies E4(n,1) and E4(n,2), which are universally linked to the energy E3(n) of the nth Efimov trimer. For infinitely large (133)Cs-(6)Li and vanishing (133)Cs-(133)Cs scattering lengths, we find (E4(1,1)/E3(1))(1/2)≈1.51 and (E4(1,2)/E3(1))(1/2)≈1.01. The (133)Cs-(6)Li scattering lengths at which these states merge with the four-atom threshold, the dependence of these energy ratios on the mass ratio between the heavy and light atoms, and selected aspects of the generalized Efimov scenario for N>4 are also discussed. Possible implications of our results for ongoing cold atom experiments are presented.