Multichannel effects in the Efimov regime from broad to narrow Feshbach resonances

We study Efimov physics of three identical bosons with pairwise multichannel interactions for Feshbach resonances of adjustable width. We find that the two-body multichannel nature of the interaction can affect the universal three-body spectrum, especially for resonances of intermediate width. The shifts in this universal spectrum are caused by trimer states in the closed interaction channels that couple to the universal Efimov states. However, in the narrow resonance limit we find that the Efimov spectrum is set by the resonance width parameter r∗ only independent of the interaction potential considered. In the broad resonance limit all excited Efimov trimer energies approach the ones from the corresponding single-channel system for the scenarios investigated.