138 research outputs found
Quantum dot behavior in graphene nanoconstrictions
Graphene nanoribbons display an imperfectly understood transport gap. We
measure transport through nanoribbon devices of several lengths. In nanoribbons
of length greater than or equal to 250 nm we observe transport through multiple
quantum dots in series, while shorter constrictions of length less than or
equal to 60 nm display behavior characteristic of single and double quantum
dots. Dot size scales with constriction width. We propose a model where
transport occurs through quantum dots that are nucleated by background disorder
potentials in the presence of a confinement gap.Comment: published version: 24 pages, 9 figures (includes supplementary
information
Kondo effect and spin filtering in triangular artificial atoms
We study strongly correlated states in triangular artificial atoms.
Symmetry-driven orbital degeneracy of the single particle states can give rise
to an SU(4) Kondo state with entangled orbital and spin degrees of freedom, and
a characteristic phase shift . Upon application of a Zeeman
field, a purely orbital Kondo state is formed with somewhat smaller Kondo
temperature and a fully polarized current through the device. The Kondo
temperatures are in the measurable range. The triangular atom also provides a
tool to systematically study the singlet-triplet transitions observed in recent
experiments.Comment: 5 pages, 2 figure
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