64 research outputs found
The GL
After defining a meanfield by arithmetic means, using multiplicative characters of finite
fields, its Potts Hamiltonian is exactly computed. Moreover, it proves to be invariant with respect to
every change of basis in Fq over the prime field Fp
Diffusive Charge Transport in Graphene on SiO2
We review our recent work on the physical mechanisms limiting the mobility of
graphene on SiO2. We have used intentional addition of charged scattering
impurities and systematic variation of the dielectric environment to
differentiate the effects of charged impurities and short-range scatterers. The
results show that charged impurities indeed lead to a conductivity linear in
density in graphene, with a scattering magnitude that agrees quantitatively
with theoretical estimates [1]; increased dielectric screening reduces
scattering from charged impurities, but increases scattering from short-range
scatterers [2]. We evaluate the effects of the corrugations (ripples) of
graphene on SiO2 on transport by measuring the height-height correlation
function. The results show that the corrugations cannot mimic long-range
(charged impurity) scattering effects, and have too small an
amplitude-to-wavelength ratio to significantly affect the observed mobility via
short-range scattering [3, 4]. Temperature-dependent measurements show that
longitudinal acoustic phonons in graphene produce a resistivity linear in
temperature and independent of carrier density [5]; at higher temperatures,
polar optical phonons of the SiO2 substrate give rise to an activated, carrier
density-dependent resistivity [5]. Together the results paint a complete
picture of charge carrier transport in graphene on SiO2 in the diffusive
regime.Comment: 28 pages, 7 figures, submitted to Graphene Week proceeding
Effect of charged impurity correlation on transport in monolayer and bilayer graphene
We study both monolayer and bilayer graphene transport properties taking into
account the presence of correlations in the spatial distribution of charged
impurities. In particular we find that the experimentally observed sublinear
scaling of the graphene conductivity can be naturally explained as arising from
impurity correlation effects in the Coulomb disorder, with no need to assume
the presence of short-range scattering centers in addition to charged
impurities. We find that also in bilayer graphene correlations among impurities
induce a crossover of the scaling of the conductivity at higher carrier
densities. We show that in the presence of correlation among charged impurities
the conductivity depends nonlinearly on the impurity density and can even
increase with .Comment: 11 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1104.066
The surface science of quasicrystals
The surfaces of quasicrystals have been extensively studied since about 1990. In this paper we review work on the structure and morphology of clean surfaces, and their electronic and phonon structure. We also describe progress in adsorption and epitaxy studies. The paper is illustrated throughout with examples from the literature. We offer some reflections on the wider impact of this body of work and anticipate areas for future development.
(Some figures in this article are in colour only in the electronic version
Formation of atomic nanoclusters on graphene sheets
The formation of atomic nanoclusters on suspended graphene sheets have been
investigated by employing a Molecular dynamics simulation at finite
temperature. Our systematic study is based on temperature dependent Molecular
dynamics simulations of some transition and alkali atoms on suspended graphene
sheets. We find that the transition atoms aggregate and make various size
nanoclusters distributed randomly on graphene surface. We also report that most
alkali atoms make one atomic layer on graphene sheets. Interestingly, the
potassium atoms almost deposit regularly on the surface at low temperature. We
expect from this behavior that the electrical conductivity of a suspended
graphene doped by potassium atoms would be much higher than the case doped by
the other atoms at low temperature.Comment: High quality figures can be requested to the author
Transition metals on the (0001) surface of graphite: Fundamental aspects of adsorption, diffusion, and morphology
In this article, we review basic information about the interaction of transition metal atoms with the (0001) surface of graphite, especially fundamental phenomena related to growth. Those phenomena involve adatom-surface bonding, diffusion, morphology of metal clusters, interactions with steps and sputter-induced defects, condensation, and desorption. General traits emerge which have not been summarized previously. Some of these features are rather surprising when compared with metal-on-metal adsorption and growth. Opportunities for future work are pointed out
Transition metals on the (0 0 0 1) surface of graphite: Fundamental aspects of adsorption, diffusion, and morphology
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