Scaling properties of universal tetramers

We evidence the existence of a universal correlation between the binding energies of successive four-boson bound states (tetramers), for large two-body scattering lengths (a), related to an additional scale not constrained by three-body Efimov physics. Relevant to ultracold atom experiments, the atom-trimer relaxation peaks for |a|→∞ when the ratio between the tetramer and trimer energies is 4.6 and a new tetramer is formed. The new scale is also revealed for a<0 by the prediction of a correlation between the positions of two successive peaks in the four-atom recombination process. © 2011 American Physical Society.