A geometric scaling symmetry that can be found in a series of Russian nesting dolls is rarely found in nature and in physics. Nevertheless, nuclear physicist Vitaly Efimov predicted in 1970 that a geometric scaling symmetry would emerge from a series of three-body bound states when pairwise interactions are resonantly enhanced. Following Efimov’s prediction, these exotic three-body bound states, now called Efimov states, are being pursued in different physics disciplines such as nuclear, particle, and atomic physics. The observation of Efimov states in ultracold atoms was first reported in 2005, followed by many reports using different atomic species. Despite abundant observations, a model-independent observation of the geometric scaling symmetry has been elusive. In this talk, I will report the first observation of three consecutive Efimov states in an ultracold 6Li-133Cs mixture near a broad interspecies Feshbach resonance. The resonance positions follow closely a geometric progression and provide a model-independent confirmation of the discrete scaling symmetry. At the end of my talk, I will introduce a new experiment that involves a mixture of AlH+ and Rb. In this experiment, we plan to study chemical reactions in the quantum regime between the trapped molecular ions and the laser-cooled atoms. The methods developed in this experiment should be applicable to different atoms and molecules whose internal structures can be used for precision measurements, including searching for physics beyond the Standard Model.
Argonne Physics Division Seminar Schedule