Fall Semester 2012-3

In a perfect crystal the electrons move as if they are free particles with effective mass m* moving in a vacuum. Otherwise, we say that the electrons undergo collisions and are scattered. It is due to these collisions that the material is resistant to the flow of electric current. There are many scattering mechanisms which can affect the electrons, the major ones being defects in the crystal, phonons, and impurities.

The mechanism studied in this project is screened Coulomb scattering by charged impurities from the environment. The numeric calculation, following the paper by Hwang and Das Sarma[1], is based on the assumption that this is the dominant contribution to the scattering. The Ohmic resistivity of the graphene electrons is calculated by the finite-temperature Drude-Boltzmann theory. The screening effect of the impurities is treated in the random phase approximation.

After a short description of graphene and the experimental results of the temperature dependence of conductivity, there is an extensive section on the theory, and a short explanation about numerical solutions. The simulation code is available for download, and is followed by a discussion of the results.

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