Observation of Efimov Universality across a Nonuniversal Feshbach Resonance in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">K</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>39</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
Xin Xie, Michael J. Van de Graaff, Roman Chapurin, Matthew D. Frye, Jeremy M. Hutson, Jose D'Incao, Paul S. Julienne, Jun Ye, Eric Cornell
Abstract
We study three-atom inelastic scattering in ultracold ^{39}K near a Feshbach resonance of intermediate coupling strength. The nonuniversal character of such resonance leads to an abnormally large Efimov absolute length scale and a relatively small effective range r_{e}, allowing the features of the ^{39}K Efimov spectrum to be better isolated from the short-range physics. Meticulous characterization of and correction for finite-temperature effects ensure high accuracy on the measurements of these features at large-magnitude scattering lengths. For a single Feshbach resonance, we unambiguously locate four distinct features in the Efimov structure. Three of these features form ratios that obey the Efimov universal scaling to within 10%, while the fourth feature, occurring at a value of scattering length closest to r_{e}, instead deviates from the universal value.