Description:

Title: (Non-)universality of Efimov Physics in a Mass-Imbalanced System

Speaker: Jacob Johansen, University of Chicago

Abstract: In 1970, Vitaly Efimov discovered a surprising analytic solution to a three-body problem with diverging two-body interactions: despite the absence of two-body bound states, there exists an infinite series of three-body bound states. These Efimov states are notable for their predicted universal geometric scaling, with a scaling constant of 22.7 for any system of three identical bosons. These states are observable in ultracold atomic systems via Efimov resonances, as enhanced three body loss is visible where the Efimov state binding energy vanishes, and have been identified in a variety of atomic systems employing magnetic Feshbach resonances. In addition to the geometric scaling, which we recently observed by taking advantage of a reduced Efimov scaling constant in our mass imbalanced [6]Li [133]Cs system, an interesting pattern has emerged in these measurements: while expected to be non-universal, the absolute positions of Efimov resonances appear to scale simply with the van der Waals length. Theories attempting to explain this observation have predicted a dependence on the strength of the Feshbach resonance for narrow resonances, yet experiments attempting to probe this regime have so far been inconsistent with the predicted strong dependence. In this talk, I focus primarily on our recent measurements showing a dependence on Feshbach resonance strength. I directly compare two Feshbach resonances, one broad and one very narrow, which are nearly identical with the exception of the resonance strength, and find a striking difference in the first Efimov resonance position. Our measurement makes significant strides toward resolving the recent, major discrepancy between experiment and theory that exists in the field today.

Keywords: Physics, Astronomy, AMO