12,536 research outputs found
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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