Coulomb drag in graphene single layers separated by a thin spacer

Motivated by very recent studies of Coulomb drag in grahene-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 $n^{-1}\mathrm{\mid }\ln (n{d}^2)\mathrm{\mid }$ for the thin one.