|Title||Observation of Efimov Universality across a Nonuniversal Feshbach Resonance in K-39|
|Publication Type||Journal Article|
|Year of Publication||2020|
|Authors||X. Xie, M. J. Van de Graaff, R. Chapurin, M. D. Frye, J. M. Hutson, J. P. D'Incao, P. S. Julienne, J. Ye, and E. A. Cornell|
|Journal||Phys. Rev. Lett.|
We study three-atom inelastic scattering in ultracold K-39 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.