Plasmon and dielectric background inhomogeneity enhancement of Coulomb drag in graphene double-layer structures

摘要

The drag of massless fermions in graphene double-layer structures isinvestigated in a wide rage of temperatures and inter-layer separations. Weshow that the inhomogeneity of the dielectric background in such graphenestructures for experimentally relevant parameters results in a significantenhancement of the drag resistivity. At intermediate temperatures the dynamicalscreening via plasmon-mediated drag enhances the drag resistivity and resultsin an upturn in its behavior at large inter-layer separations. In a range ofinter-layer separations, corresponding to the strong-to-weak crossover couplingof graphene layers, we find that the drag resistivity decreases approximatelyquadratically with the inter-layer spacing. This dependence weakens with adecrease of the inter-layer spacing while for larger separations we recover thecubic (quartic) dependence at intermediate (low) temperatures.