Charged impurity scattering in bilayer graphene

We have examined the impact of charged impurity scattering on charge carrier transport in bilayer graphene (BLG) by deposition of potassium in ultrahigh vacuum at low temperature. Charged impurity scattering gives a conductivity which is supralinear in carrier density with a magnitude similar to single-layer graphene for the measured range of carrier densities of 2--4×10¹² cm^-2. Upon addition of charged impurities of concentration nᵢₘₚ, the minimum conductivity σₘᵢₙ decreases proportional to nᵢₘₚ^-1/2 while the electron and hole puddle carrier density increases proportional to nᵢₘₚ1/2. These results for the intentional deposition of potassium on BLG are consistent with theoretical predictions for charged impurity scattering assuming a gapless hyperbolic dispersion relation. However, our results also suggest that charged impurity scattering alone cannot explain the observed transport properties of pristine BLG on SiO₂ before potassium doping.