Tunable adsorbate-adsorbate interactions on graphene.

We propose a mechanism to control the interaction between adsorbates on graphene. The interaction between a pair of adsorbates--the change in adsorption energy of one adsorbate in the presence of another--is dominated by the interaction mediated by graphene's π electrons and has two distinct regimes. Ab initio density functional, numerical tight-binding, and analytical calculations are used to develop the theory. We demonstrate that the interaction can be tuned in a wide range by adjusting the adsorbate-graphene bonding or the chemical potential.