(a) Binding energy as a function of the dimensionless interaction parameter G defined in the text. The solid line is the plot of Eq. (13) and dashed line is for the analytical results in the weakly interacting limit presented in Ref. [46]. The red dot denotes the critical interaction parameter beyond which a bound state will form. (b) Critical interaction parameter as a function of the lattice potential parameter t (Eq. (14).