11,489 research outputs found
Role of Self-Interaction Effects in the Geometry Optimization of Small Metal Clusters
By combining the Self-Interaction Correction (SIC) with pseudopotential
perturbation theory, the role of self-interaction errors inherent to the Local
Density Approximation (LDA) to Density Functional Theory is estimated in the
determination of ground state and low energy isomeric structures of small
metallic clusters. Its application to neutral sodium clusters with 8 and 20
atoms shows that the SIC provides sizeable effects in Na_8, leading to a
different ordering of the low lying isomeric states compared with ab-initio LDA
predictions, whereas for Na_20, the SIC effects are less pronounced, such that
a quantitative agreement is achieved between the present method and ab-initio
LDA calculations.Comment: RevTeX, 4 pages, 1 figure available from [email protected]
Lorentz invariance for mixed neutrinos
We show that a proper field theoretical treatment of mixed (Dirac) neutrinos
leads to non-trivial dispersion relations for the flavor states. We analyze
such a situation in the framework of the non-linear relativity schemes recently
proposed by Magueijo and Smolin. We finally examine the experimental
implications of our theoretical proposals by considering the spectrum and the
end-point of beta decay in tritium.Comment: 8 pages, 4 figures. Presented at 2nd International Workshop DICE2004:
From Decoherence and Emergent Classicality to Emergent Quantum Mechanics,
Castello di Piombino, Tuscany, Italy, 1-4 Sep 200
Persistent current magnification in a double quantum-ring system
The electronic transport in a system of two quantum rings side-coupled to a
quantum wire is studied via a single-band tunneling tight-binding Hamiltonian.
We derived analytical expressions for the conductance, density of states and
the persistent current when the rings are threaded by magnetic fluxes. We found
a clear manifestation of the presence of bound states in each one of those
physical quantities when either the flux difference or the sum of the fluxes
are zero or integer multiples of a quantum of flux. These bound states play an
important role in the magnification of the persistent current in the rings. We
also found that the persistent current keeps a large amplitude even for strong
ring-wire coupling.Comment: 15 pages, 10 figures. Submitted to PR
Electron Confinement Induced by Diluted Hydrogen-like Ad-atoms in Graphene Ribbons
We report the electronic properties of two-dimensional systems made of
graphene nanoribbons which are patterned with ad-atoms in two separated
regions. Due to the extra electronic confinement induced by the presence of the
impurities, we find resonant levels, quasi-bound and impurity-induced localized
states, which determine the transport properties of the system. Regardless of
the ad-atom distribution in the system, we apply band-folding procedures to
simple models and predict the energies and the spatial distribution of those
impurity-induced states. We take into account two different scenarios: gapped
graphene and the presence of randomly distributed ad-atoms in a low dilution
regime. In both cases the defect-induced resonances are still detected. Our
findings would encourage experimentalist to synthesize these systems and
characterize their quasi-localized states employing, for instance, scanning
tunneling spectroscopy (STS). Additionally, the resonant transport features
could be used in electronic applications and molecular sensor devices.Comment: 12 pages, 11 figures, submitted (minor changes
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