The phase diagram of the first layer of He4 adsorbed on a single graphene sheet was calculated by a series of diffusion Monte Carlo calculations including corrugation effects. Since the number of C-He interactions was smaller than in graphite, the binding energy of He4 atoms to graphene was reduced approximately 13.4K per helium atom. The results indicated that the phase diagram was qualitatively similar to that of helium on graphite. A two-dimensional liquid film on graphene was predicted to be metastable with respect to the commensurate solid but the difference in energy between both phases was very small, opening the possibility of such a liquid film to be experimentally observed.

He4 on a Single Graphene Sheet. Gordillo, M.C., Boronat, J.: Physical Review Letters, 2009, 102[8], 085303