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Rémi Avriller

Theoretical modelling of quantum transport in carbon nanotube-based devices

Published on 25 September 2008

Thesis presented September 25, 2008

Carbon nanotubes are quasi-1D structures obtained by rolling a graphene sheet onto a cylinder surface. This determines the chirality and the complete electronic and vibrational band structure of carbon nanotubes. However, due to low dimensionality of such systems and to the wave nature of electrons, this band structure is strongly modified by applying an external magnetic field, and broken by a random disordered potential (loss of translational invariance), or by excitation of an inelastic mechanism (electron-phonon interaction). The aim of the following thesis is to explore quantum transport properties in carbon nanotubes, due to the interplay between quantum interferences and interaction processes. We will focus ourselves on disordered carbon nanotubes doped by nitrogen or boron atoms, modelize the disordered hamiltonian and probe scaling laws of conductance. We will also consider the role of a uniform and static magnetic field on transport regimes at low bias(Landau level formation and Aharonov-Bohm oscillation). Inelastic collisions due to electron-optic phonon coupling will finally be considered. Due to the low dimensionality of carbon nanotubes, the adiabatic approximation fails and a proper transport formalism in Fock space of electrons and phonons has to be considered. In the former studies, an effective microscopic hamiltonian is built and the problem of coherent quantum transport solved numerically or analytically.

Carbon nanotubes, disordered low dimensional systems, mesoscopic physics, coherent electronic transport, inelastic transport, electron-phonon interaction, high magnetic fields

On-line thesis.