# Universal three-body recombination and Efimov resonances in an ultracold Li-Cs mixture

### J. Ulmanis 1 S. Häfner 1 R. Pires 1 F. Werner 2 D. S. Petrov 3 E. D. Kuhnle 1 M. Weidemüller 4, 1

#### Physical Review A, American Physical Society, 2016, 93, pp.022707

We study Efimov resonances via three-body loss in an ultracold two-component gas of fermionic $^6$Li and bosonic $^{133}$Cs atoms close to a Feshbach resonance at 843~G, extending results reported previously [Pires \textit{et al.}, Phys. Rev. Lett. 112, 250404 (2014)] to temperatures around 120~nK. The experimental scheme for reaching lower temperatures is based upon compensating the gravity-induced spatial separation of the mass-imbalanced gases with bichromatic optical dipole traps. We observe the first and second excited Li-Cs-Cs Efimov resonance in the magnetic field dependence of the three-body event rate constant, in good agreement with the universal zero-range theory at finite temperature [Petrov and Werner, Phys. Rev. A 92, 022704 (2015)]. Deviations are found for the Efimov ground state, and the inelasticity parameter $\eta$ is found to be significantly larger than those for single-species systems.

• 1. Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg
• 2. LKB [Collège de France] - Laboratoire Kastler Brossel
• 3. LPTMS - Laboratoire de Physique Théorique et Modèles Statistiques
• 4. Hefei National Laboratory for Physical Sciences at the Microscale