The Efimov scenario, where pairwise resonantly interacting particles form an infinite geometrical series of bound three-body states, the Efimov states, is one of the most fundamental effects in modern few-body quantum physics. The theoretical understanding and experimental observation of such progressions in both homonuclear and heteronuclear systems has been a longstanding challenge that requires exquisite control and tuning of mutual particle interactions and appropriate treatment of internal and external degrees of freedom. Here, employing a drastic reduction of the geometrical scaling factor due to the high mass imbalance of Li and Cs atoms, we present the first observation of three consecutive LiCsCs Efimov resonances via three body recombination rate measurements [1]. The previous analysis of Feshbach resonances [2] is extended with radiofrequency association of LiCs Feshbach molecules to obtain precise mapping of the appliedmagnetic field onto the scattering length [3]. This new parametrization of Li-Cs interaction properties is used to compare the measured recombination spectra, including Efimov resonance positions and scaling factors,with state-of-the-art few-body theories. These findings are used to elucidate the connection between theuniversal regime that is excellently approximated by two-body contact interactions and the short range dominated regime, which is described by the van der Waals tails of pairwise interaction potentials [4-6].
*Work done in collaboration with Juris Ulmanis, Stephan Häfner, Rico Pires, and Eva Kuhnle (U Heidelberg), Chris Greene (Purdue U) and Yujun Wang (Kansas State U).
[1] R. Pires, J. Ulmanis, S. Häfner, E. D. Kuhnle and M. Weidemüller, Phys. Rev. Lett. 112, 250404
(2014).
[2] R. Pires, J. Ulmanis, M. Repp, E. D. Kuhnle, M. Weidemüller, T. Tiecke, B. Ruzic, C. Greene, J.
Bohn and E. Tiemann, Phys. Rev. A 90, 012710 (2014).
[3] J. Ulmanis, S. Häfner, R. Pires, E. D. Kuhnle, M. Weidemüller, E. Tiemann, New J. Phys. 17,
055009 (2015).
[4] J. Ulmanis et al., Phys. Rev. A 93, 022707 (2016).
[5] J. Ulmanis et al., Phys. Rev. Lett. 117, 153201 (2016).
[6] S. Häfner et al., Phys. Rev. A 95, 062708 (2017).
[7] For a review, see: J. Ulmanis et al., National Science Reviews 3, 174 (2016).