Heat flow in metallic carbon nanostructures: hot phonons or hot electrons?

A model for electronic and thermal transport in metallic carbon nanotubes and graphene ribbons under electrical stress is presented. The influence of acoustic and optical phonon scattering is taken into account within a self-consistent electro-thermal scheme. Owing to the linear electronic dispersion relation, two thermalized carrier populations arise as a consequence of inter-carrier scattering. We show that depending on the experimental setup and nanotube parameters, different transport regimes emerge for which non-equilibrium electrons and phonons compete to carry the energy in these carbon nanostructures.