Efimov trimers in Lithium 6

Three atoms can form unusual three-body bound states called Efimov trimers due to a universal attraction arising whenever the scattering lengths between the atoms are much larger than the range of their interactions. Various indirect signatures and first-time direct spectroscopy of such Efimov trimers have been demonstrated in recent experiments [1] using lithium 6 in three different spin states, where the scattering lengths are enhanced by magnetic Feshbach resonances. We found that all these measurements are indeed consistent with the universal Efimov effect, but non-universal deviations at negative energy remain to be understood and have been quantified by a variation of a short-range 3-body paramater [2].\\[4pt] [1] T. B. Ottenstein et al., Phys. Rev. Lett. {\bf 101}, 203202 (2008); J. H. Huckans et al., Phys. Rev. Lett. {\bf 102}, 165302 (2009); S. Nakajima, et al., Phys. Rev. Lett. {\bf 105}, 023201 (2010); T. Lompe et al., Phys. Rev. Lett. {\bf 105}, 103201, 2010); T. Lompe et al., Science {\bf 330}, 940 (2010).\\[0pt] [2] P. Naidon and M. Ueda, arXiv:1008.2260 (2010); S. Nakajima, M. Horikoshi, T. Mukaiyama, P. Naidon, and M. Ueda, arXiv:1010.1954 (2010).