title: Microscopic origin and universality classes of the Efimov three-body parameter.
abstract: The low-energy spectrum of three particles interacting via nearly resonant two-body interactions in the Efimov regime is set by the so-called three-body parameter. We show that the three-body parameter is essentially determined by the zero-energy two-body correlation. As a result, we identify two classes of two-body interactions for which the three-body parameter has a universal value in units of their effective range. One class involves the universality of the three-body parameter recently found in ultracold atom systems. The other is relevant to short-range interactions that can be found in nuclear physics and solid-state physics.
authors.affiliation: RIKEN Nishina Centre, RIKEN, Wakō 351-0198, Japan.
authors.forename: Pascal
authors.initials: P
authors.lastname: Naidon
authors.affiliation: Department of Physics, University of Tokyo, 7-3-1 Hongō, Bunkyō-ku, Tōkyō 113-0033, Japan.
authors.forename: Shimpei
authors.initials: S
authors.lastname: Endo
authors.affiliation: Department of Physics, University of Tokyo, 7-3-1 Hongō, Bunkyō-ku, Tōkyō 113-0033, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Ueda