Coulomb drag in graphene single layers separated by a thin spacer

Motivated by very recent studies of Coulomb drag in a graphene-BN-graphene system we develop a theory of Coulomb drag for the Fermi-liquid regime, for the case when the ratio of spacer thickness d to the Fermi wavelength of electrons is arbitrary. The concentration (n) and thickness dependence of the drag resistivity is changed from n(-3)d(-4) for the thick spacer to n(-1) vertical bar ln (nd(2))vertical bar for the thin one.