Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
2007-05-10
Proc. Natl. Acad. Sci. USA 104, 18392 (2007)
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
To be published in Proc. Natl. Acad. Sci. USA
Scientific paper
10.1073/pnas.0704772104
We demonstrate theoretically that most of the observed transport properties of graphene sheets at zero magnetic field can be explained by scattering from charged impurities. We find that, contrary to common perception, these properties are not universal but depend on the concentration of charged impurities $n_{\rm imp}$. For dirty samples ($250 \times 10^{10} {\rm cm}^{-2} < n_{\rm imp} < 400 \times 10^{10} {\rm cm}^{-2}$), the value of the minimum conductivity at low carrier density is indeed $4 e^2/h$ in agreement with early experiments, with weak dependence on impurity concentration. For cleaner samples, we predict that the minimum conductivity depends strongly on $n_{\rm imp}$, increasing to $8 e^2/h$ for $n_{\rm imp} \sim 20 \times 10^{10}{\rm cm}^{-2}$. A clear strategy to improve graphene mobility is to eliminate charged impurities or use a substrate with a larger dielectric constant.
Adam Shaffique
Galitski Victor
Hwang Euyheon H.
Sarma Sankar Das
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