Electron-electron interactions are shown to cause charge accumulation at the edges of a graphene nanoribbon and also formation of edge states even without magnetic field. The edge states form gradually as the Fermi energy or electron concentration increases. They are immune to defects in interior of a device but can be easily scattered by an edge imperfection. A narrow trench blocks transmission almost completely but for sufficiently long and smooth constriction having a cosine shape the transmission can be improved.
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