Effect of gap fluctuations on conductance of monolayer and bilayer graphene superlattices

• Gap fluctuations causes to disappearance the Klein tunneling in monolayer graphene.
• Gap fluctuations causes to decreasing the conductance of graphene superlattices (GSL).
• In monolayer GSL the critical gaps for which T=1T=1, wash out when Gap fluctuations turn on.
• Gap fluctuations affect the conductance of monolayer GSL more than the bilayer GSL.
• The size of GSL affects the transmission of Dirac fermions in GSL.

We study numerically the effect of gap fluctuations on transmission and conductance of the monolayer and bilayer graphene superlattices. The system consists of a sequence of electron doped graphene as wells and hole doped graphene as barriers. Because of random nature of experimental technique, the fluctuations are generate in the energy gap applied in graphene. We show that the gap fluctuations cause to disappearing the Klein tunneling in monolayer graphene. So, for normal incident electrons in the superlattice, the transmission of electrons is not unity when the fluctuations are turn on. Also, the conductance of the system decreases with increasing the strength of disorder. In the case of bilayer graphene superlattice the same as monolayer, the transmission of electrons and conductance of the superlattice decreases with increasing of the strength of disorder. Also, we studied the size effect of superlattice on the transmission of electrons of monolayer and bilayer graphene.