%0 Journal Article
%T Universality of the three-body Efimov parameter at narrow Feshbach resonances
%A Sanjukta Roy
%A Manuele Landini
%A Andreas Trenkwalder
%A Giulia Semeghini
%A Giacomo Spagnolli
%A Andrea Simoni
%A Marco Fattori
%A Massimo Inguscio
%A Giovanni Modugno
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevLett.111.053202
%X We measure the critical scattering length for the appearance of the first three-body bound state, or Efimov three-body parameter, at seven different Feshbach resonances in ultracold 39K atoms. We study both intermediate and narrow resonances, where the three-body spectrum is expected to be determined by the non-universal coupling of two scattering channels. We observe instead approximately the same universal relation of the three-body parameter with the two-body van der Waals radius already found for broader resonances, which can be modeled with a single channel. This unexpected observation suggests the presence of a new regime for three-body scattering at narrow resonances.
%U http://arxiv.org/abs/1303.3843v1