▎ 摘　　要

Using quantum Monte Carlo we have studied the superfluid density of the first layer of He-4 and H-2 adsorbed on graphene and graphite. Our main focus has been on the equilibrium ground state of the system, which corresponds to a registered root 3 x root 3 phase. The perfect solid phase of H-2 shows no superfluid signal, whereas He-4 has a finite but small superfluid fraction (0.67%). The introduction of vacancies in the crystal makes the superfluidity increase, showing values as large as 14% in He-4 without destroying the spatial solid order.