  The Efimov effect in heteronuclear cold atomic systems is experimentally more
easily accessible than the Efimov effect for identical atoms, because of the
potentially smaller scaling factor. We focus on the case of two or three heavy
identical bosons and another atom. The former case was recently observed in a
mixture of 133Cs and 6Li atoms. We employ the Gaussian Expansion Method as
developed by Hiyama, Kino et al.. This is a variational method that uses
Gaussians that are distributed geometrically over a chosen range. Supplemental
calculations are performed using the Skorniakov-Ter-Martirosian equation. Blume
et al. previously investigated the scaling properties of heteronuclear systems
in the unitary limit and at the three-body breakup threshold. We have completed
this picture by calculating the behaviour on the positive scattering length
side of the Efimov plot, focussing on the dimer threshold.
