48,955 research outputs found
Sublattice asymmetry of impurity doping in graphene: A review
In this review we highlight recent theoretical and experimental work on
sublattice asymmetric doping of impurities in graphene, with a focus on
substitutional Nitrogen dopants. It is well known that one current limitation
of graphene in regards to its use in electronics is that in its ordinary state
it exhibits no band gap. By doping one of its two sublattices preferentially it
is possible to not only open such a gap, which can furthermore be tuned through
control of the dopant concentration, but in theory produce quasi-ballistic
transport of electrons in the undoped sublattice, both important qualities for
any graphene device to be used competetively in future technology. We outline
current experimental techniques for synthesis of such graphene monolayers and
detail theoretical efforts to explain the mechanisms responsible for the
effect, before suggesting future research directions in this nascent field.Comment: 20 pages, 4 figures. Accepted for publication in Beilstein Journal of
Nanotechnolog
Exchange coupling between magnetic layers across non-magnetic superlattices
The oscillation periods of the interlayer exchange coupling are investigated
when two magnetic layers are separated by a metallic superlattice of two
distinct non-magnetic materials. In spite of the conventional behaviour of the
coupling as a function of the spacer thickness, new periods arise when the
coupling is looked upon as a function of the number of cells of the
superlattice. The new periodicity results from the deformation of the
corresponding Fermi surface, which is explicitly related to a few controllable
parameters, allowing the oscillation periods to be tuned.Comment: 13 pages; 5 figures; To appear in J. Phys.: Cond. Matte
Analysis of a class of boundary value problems depending on left and right Caputo fractional derivatives
In this work we study boundary value problems associated to a nonlinear fractional ordinary differential equation involving left and right Caputo derivatives. We discuss the regularity of the solutions of such problems and, in particular, give precise necessary conditions so that the solutions are C1([0, 1]). Taking into account our analytical results, we address the numerical solution of those problems by the augmented-RBF method. Several examples illustrate the good performance of the numerical method.P.A. is partially supported by FCT, Portugal, through the program “Investigador FCT” with reference IF/00177/2013 and the scientific projects PEstOE/MAT/UI0208/2013 and PTDC/MAT-CAL/4334/2014. R.F. was supported by the “Fundação para a Ciência e a Tecnologia (FCT)” through the program “Investigador FCT” with reference IF/01345/2014.info:eu-repo/semantics/publishedVersio
Dispersion and damping of multi-quantum well polaritons from resonant Brillouin scattering by folded acoustic modes
We report on confined exciton resonances of acoustic and folded acoustic
phonon light scattering in a GaAs/AlAs multi-quantum-well. Significant
variations of the line shifts and widths are observed across the resonance and
quantitatively reproduced in terms of the polariton dispersion. This high
resolution Brillouin study brings new unexpectedly detailed informations on the
polariton dynamics in confined systems
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