³He dimers in two-dimensional ³He–⁴He mixture films

Ground state properties of the two-dimensional ³He–⁴He mixture are studied at zero temperature. We find that at low concentrations ³He atoms dimerize and form bosonic mixture with ⁴He. The binding energy of the dimer ranges from 10⁻³ K near the saturation density to 10⁻⁶ K at the solidification density. The radius of such a weakly bound dimer is tens of Ångströms. A stable atomic mixture is found at concentration larger than ≈5% varying with density. At high ³He concentrations the mixture phase separates and critical concentrations are obtained by calculating the second derivative of the enthalpy.