Efimov and non-Efimov physics of 2+1 particles

Three-body bound states called Efimov states are associated with remarkable features such as discrete scale invariance of their spectrum, and have attracted a lot of interest since their recent experimental realizations with ultracold atoms [1]. These states are characterized by the scattering length between particles and a short-range parameter. Recently, however, universal trimers [2] which depend only on the scattering length have been theoretically predicted for systems of two heavy and one light particles. Although the origin of these trimers is closely related to the Efimov effect, they have a distinct nature. We will discuss on the relationship between these universal trimers and Efimov trimers.\\[4pt] [1] F. Ferlaino, and R. Grimm, Physics, {\bf 3}, 9 (2010)\\[0pt] [2] O. I. Kartavtsev, and A. V. Malykh, J. Phys. B, {\bf 40}, 1429 (2007).