Computational Studies of Defects in Nanoscale Carbon Materials
Graphene nanostructures: Edges, ribbons, superlattices, and defective tubes
In this talk, I discuss some of our recent work using theory and computation to study the electronic, optical and transport properties of sp2-bonded carbon nanostructures, including those with defects and under external perturbations. Systems investigated include defective carbon nanotubes, graphene, graphene nanoribbons, and graphene subjected to nanoscale external periodic potentials (called graphene superlattices). These nanostructures exhibit a number of unexpected behaviors novel conductance characteristics, magnetic defect states, extraordinarily large excitonic effects in their optical response, anomalous behaviors in the dynamics of carriers (the 2D massless Dirac fermions) in graphene superlattices, and an electric field-induced half-metallic state for zigzag graphene nanoribbons, among others. Moreover, under specific conditions, graphene superlattices are predicted to be electron supercollimators and new generation of 2D massless Dirac fermions may be created. The physical origins of these interesting properties and phenomena are discussed.