Electronic Transport of Nanographene: Effect of Geometry and Edges

Date & Time
10 June 2009 (Wed) 3:30 pm - 5:00 pm
8F large seminar room, SENGEN site
Dr. Katsunori Wakabayashi (若林 克法 博士)
NIMS-MANA & JST-PRESTO(NIMS国際ナノアーキテクトニクス研究拠点・JSTさきがけ)
Electronic Transport of Nanographene: Effect of Geometry and Edges
The successive fabrication of graphene devices has has initiated intensive and diverse research on carbon related systems. The honeycomb crystal structure of single layer graphene consists of two nonequivalent sublattices and results in a unique band structure for the itinerant p-electrons near the Fermi energy which behave as massless Dirac fermion. In graphene, the presence of edges can have strong implications for the spectrum of the p-electrons. In graphene nanoribbons with zigzag edges, localized states appear at the edge with energies close to the Fermi level. In contrast, edge states are absent for ribbons with armchair edges. Recent experiments have succeeded to synthesize graphene nanoribbons using lithography techniques and chemical techniques. In my talk, we focus on edge and geometry effects of the electronic transport properties of graphene nanoribbons. (1) In zigzag nanoribbons, for disorder without inter-valley scattering a single perfectly conducting channel emerges associated with such a chiral mode due to edge states, i.e. the absence of the localization. (2) In armchair nanoribbons, the single-channel transport subjected to long-ranged impurities is nearly perfectly conducting, where the backward scattering matrix elements in the lowest order vanish as a manifestation of internal phase structures of the wavefunction. (3) Nano-graphene junctions are shown to have the zero-conductance anti-resoances associated with the edge states. The relation between the condition of the resonances and geometry is discussed.
Dr. Yoshitaka Tateyama(館山佳尚)