Drag effect of electrons in a system of two graphene layers

The drag effect of charge carriers in the system of two graphene layers separated by insulator that is caused by interlayer tunneling is considered. For description of interlayer tunneling the model of randomly positioned tunnel bridges is used. The dependence of transresistivity of the system on the tunnel bridge size for different mutual orientations of graphene layers (hexagonal and Bernal orientations) was calculated. We found that for the Bernal orientation, the transresistivity is sensitive to the tunneling bridge size and tends to zero in the point contact limit. For the hexagonal orientation, the transresistivity weakly depends on the tunneling bridge size. In both cases, the transresistivity of the system strongly depends on the longitudinal magnetic field strength and the difference between the Fermi energies of quasiparticles of graphene layers. This allows one to separate directly in experiments the contribution to the transresistivity caused by tunneling.