Nonuniversal Efimov Atom-Dimer Resonances in a Three-Component Mixture of ${}^6\mathrm{Li}$

We observed an enhanced atom-dimer loss due to the existence of Efimov states in a three-component mixture of ${}^6\mathrm{Li}$ atoms. We measured the magnetic-field dependence of the atom-dimer loss in the mixture of atoms in state $|1⟩$ and dimers formed in states $|2⟩$ and $|3⟩$, and found two peaks corresponding to the degeneracy points of the energy levels of $|23⟩$ dimers and the ground and first excited Efimov trimers. We found that the locations of these peaks disagree with universal theory predictions, in a way that cannot be explained by nonuniversal two-body properties. We constructed theoretical models that characterize the nonuniversal three-body physics of three-component ${}^6\mathrm{Li}$ atoms in the low-energy domain.

Figure 1

Binding energies $E_b$ of the dimer and trimer states in a three-component mixture of ${}^6\mathrm{Li}$. Dashed curves represent the universal theory predictions. Solid curves for dimers are obtained from two-body coupled-channel calculations. Solid curves for trimers are obtained from our nonuniversal models whose three-body parameter is best fitted to the experimental data. The inset shows the dimer-trimer crossing near 685 G. Dotted curves correspond to nonuniversal models without adjustment of the three-body parameter.

Figure 2

(a) Experimental procedure to prepare atom-dimer mixtures by using a multiple-stage adiabatic rapid passage (see text). Because the dimers cannot be imaged by resonance light, we dissociate the dimers by applying a magnetic-field pulse to check the population balance of the atoms and dimers. (b) and (c): Typical time evolution of the number of atoms in state $|1⟩$ at 660 and 595 G. The blue dotted curve shows an analytic fitting function assuming the pure two-body loss and the black solid curve is obtained by a numerical fitting that includes the effect of dimer-dimer loss. Gray dashed curves show time evolution of the numbers of molecules calculated from the rate equations.

Figure 3

Magnetic-field dependence of the atom-dimer loss coefficient $\beta$ (red circles) and dimer-dimer loss coefficient $\alpha$ (blue diamonds) in a mixture of atoms in state $|1⟩$ and dimers of $|23⟩$. The black dashed curve is the calculated $\beta$ from UT. The red solid curve and blue dotted curve show the $\beta$ values calculated from our nonuniversal models A and B, respectively.