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Résumé |
Relativistic massless charged particles in a two-dimensional conductor can be guided by a one-dimensional
electrostatic potential, in an analogous manner to light guided by an optical fiber. In this seminar, I will
present how we use a carbon nanotube to generate such a guiding potential in graphene and create a single
mode electronic waveguide. In our architecture, the nanotube and graphene are separated by a few
nanometers and can be controlled and measured independently. As we charge the nanotube close to the
surface of graphene, we observe in the latter the formation of a single guided mode that we detect using the
same nanotube as a probe.
I will discuss why the small dimensions of the nanotube and the linear dispersion relation of Dirac fermions
gives these electronic waveguides promising characteristics for potential applications.
I will also show that, in presence of magnetic field, our electronic waveguides host discrete electronic levels
resembling Landau levels of 2D Dirac particles but with no C-symmetric counterpart, i.e. they exist only for
one sign of energy, positive or negative, depending on the voltage applied on the nanotube. This unusual
behavior is a generic signature of Dirac surface states, which are predicted to be protected to a great extent
to surface disorder.
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