Nonuniversal Efimov Atom-Dimer Resonances in a Three-Component Mixture ofLi6

Abstract

We observed an enhanced atom-dimer loss due to the existence of Efimov states in a three-component mixture of 6Li 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 6Li atoms in the low-energy domain.

Measurement of an Efimov Trimer Binding Energy in a Three-Component Mixture ofLi6

“…In particular, we observed the temperature dependence of the RF spectrum, and found a resonance shift with temperature. Operating at lower temperature to eliminate this shift, we found that the measured energies significantly deviate from those of Ref.[16] and the previous predictions [13]. Refining the model to fit these measurements, we obtain a non-monotonic energy dependence of the three-body parameter Λ.…”

“…[16] and the previous predictions [13]. Refining the model to fit these measurements, we obtain a non-monotonic energy dependence of the three-body parameter Λ.…”

“…For example, the shift of the atom-dimer loss peaks from that expected from the three-body loss peaks [5,13,14] and the notable discrepancies in properties of the Efimov resonances between regions of positive and negative scattering lengths [8] do not seem to be consistent with a fixed three-body parameter. Therefore, the precise determination of the three-body parameter is crucial to understand these systems.To understand the atom-dimer loss feature in the threecomponent gas of 6 Li, we constructed a nonuniversal model by taking into account the energy dependence of the scattering length due to finite-range corrections [13]. This two-body physics correction still does not explain the atom-dimer loss feature that we observed experimentally.…”

“…Owing to magnetic Feshbach resonances [2], ultracold atomic systems turned out to be the first systems where the Efimov effect was observed conclusively. Since the first experimental evidence in an ultracold cesium gas [3], general properties of few-body systems near unitarity such as the universal scaling laws [4] were confirmed in many ultracold bosonic systems [5-9] and a three-component fermionic gas of 6 Li [10][11][12][13][14], via the inelastic collision enhancements and minima occurring at particular intensities of an externally-applied magnetic field. Although these features are qualitatively explained by Efimov's universal theory (UT) [4], their relative positions of loss features are shifted significantly from universal predictions.…”

Three-body parameter for Efimov states inLi6

“…The scattering length has a pole at resonance, corresponding to a two-body bound state exactly at threshold. Signatures of Efimov states were first observed in an ultracold gas of cesium atoms [7] and have since been found in many other systems, including other bosonic gases [8][9][10][11][12][13], three-component fermionic spin mixtures [14][15][16][17], and mixtures of atomic species [18][19][20][21]. Moreover, extensions of the Efimov scenario to universal states of larger clusters [22][23][24] have been demonstrated in experiments [9,25,26], highlighting the general nature of universal few-body physics.…”