Negative differential resistance in hybrid carbon-based structures

Here we study negative differential resistance effect in hybrid carbon nanostructures composed of graphene nanoribbons and carbon nanotubes. In the coupled structure, the finite flakes of nanotubes allow the formation of resonant states in the system tuning the conductance and generating Fano antiresonances. A single-band tight-binding approximation is adopted, and the density of states and conductance of the hybrid systems are calculated within the Green's function formalism and recursive numerical approaches. Armchair and zigzag edge geometries are chosen to investigate the topology effects on the electronic and transport properties for different configurations of the hybrid systems. For nanoribbons with armchair edges we derive a multiple-mode approach to analytically calculate the transmission function for the hybrid coupled system. Large and robust negative differential resistance effects are observed in the nanotube-nanoribbon zigzag hybrids that may be used in switching electronic transport responses.