Efimovian Fano-Feshbach resonances in mass-imbalanced atom-dimer gases

Three-body collisions in a two-species ultracold gas facilitate an ideal platform for the exploration of unique attributes in the Efimov physics. For example, theoretical studies on mass-imbalanced three-body collisions have demonstrated that the opposite sign of the intra- and inter-species scattering lengths results into recombination spectra which exhibit Efimov resonances intertwined with Stueckelberg destructive interference effects. In this work, we exploit these unique attributes of Efimov physics in mass-imbalanced systems by investigating the relevant scattering processes in atom-dimer gases. In particular, our analysis shows that the corresponding atom-dimer collisions are strongly enhanced when an Efimov bound state from the energetically closed three-body channel lies in the atom-dimer continuum, i.e. energetically open channel. Namely, our study demonstrates that in mass-imbalanced atom-dimer gases exists a series of atom-dimer resonances which fulfill a Fano-Feshbach scenario. In addition, we highlight the pivotal role of Stueckelberg physics on the width of the atom-dimer resonances where by adjusting the intra-species scattering length the atom-dimer continuum fully decouples from the Efimov states. Finally, our analysis addresses the universal aspects of this type of atom-dimer resonances, as well as, the importance of the Van der Waals physics.