45,554 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
Origin of the mixed-order transition in multiplex networks: the Ashkin-Teller model
Recently, diverse phase transition (PT) types have been obtained in multiplex
networks, such as discontinuous, continuous, and mixed-order PTs. However, they
emerge from individual systems, and there is no theoretical understanding of
such PTs in a single framework. Here, we study a spin model called the
Ashkin-Teller (AT) model in a mono-layer scale-free network; this can be
regarded as a model of two species of Ising spin placed on each layer of a
double-layer network. The four-spin interaction in the AT model represents the
inter-layer interaction in the multiplex network. Diverse PTs emerge depending
on the inter-layer coupling strength and network structure. Especially, we find
that mixed-order PTs occur at the critical end points. The origin of such
behavior is explained in the framework of Landau-Ginzburg theory.Comment: 10 pages, 5 figure
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