31,153 research outputs found
Carrier transport in 2D graphene layers
Carrier transport in gated 2D graphene monolayers is theoretically considered
in the presence of scattering by random charged impurity centers with density
. Excellent quantitative agreement is obtained (for carrier density ) with existing experimental data (Ref.
\onlinecite{kn:novoselov2004, kn:novoselov2005, kn:zhang2005, kn:kim2006,
kn:fuhrer2006}). The conductivity scales linearly with in the theory,
and shows extremely weak temperature dependence. The experimentally observed
asymmetry between electron and hole conductivities is explained by the
asymmetry in the charged impurity configuration in the presence of the gate
voltage, while the high-density saturation of conductivity for the highest
mobility samples is explained as a crossover between the long-range and the
point scattering dominated regimes. We argue that the experimentally observed
saturation of conductivity at low density arises from the charged impurity
induced inhomogeneity in the graphene carrier density which becomes severe for
.Comment: 5 pages, 4 figures, published in Phys. Rev. Let
Graphene magnetoresistance in a parallel magnetic field: Spin polarization effect
We develop a theory for graphene magnetotransport in the presence of carrier
spin polarization as induced, for example, by the application of an in-plane
magnetic field () parallel to the 2D graphene layer. We predict a negative
magnetoresistance for intrinsic graphene, but for
extrinsic graphene we find a non-monotonic magnetoresistance which is positive
at lower magnetic fields (below the full spin-polarization) and negative at
very high fields (above the full spin-polarization). The conductivity of the
minority spin band electrons does not vanish as the minority carrier
density () goes to zero. The residual conductivity of electrons at
is unique to graphene. We discuss experimental implications of our
theory.Comment: 5 pages, 3 figure
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