Ultracold heteronuclear three-body systems: How diabaticity limits the universality of recombination into shallow dimers

The mass-imbalanced three-body recombination process that forms a shallow dimer is shown to possess a rich Efimov-St\"uckelberg landscape, with corresponding spectra that differ fundamentally from the homonuclear case. A semi-analytical treatment of the three-body recombination predicts an unusual spectra with intertwined resonance peaks and minima, and yields in-depth insight into the behavior of the corresponding Efimov spectra. In particular, the patterns of the Efimov-St\"uckelberg landscape are shown to depend inherently on the degree of diabaticity of the three-body collisions, which strongly affects the universality of the heteronuclear Efimov states.