Electronic Transport through Carbon Nanotubes: Effects of Structural Deformation and Tube Chirality

Atomistic simulations using a combination of classical force field and density-functional theory (DFT) show that carbon atoms remain essentially ${\mathrm{sp}}^2$ coordinated in either bent tubes or tubes pushed by an atomically sharp atomic-force microscope (AFM) tip. Subsequent Green's-function-based transport calculations reveal that for armchair tubes there is no significant drop in conductance, while for zigzag tubes the conductance can drop by several orders of magnitude in AFM-pushed tubes. The effect can be attributed to simple stretching of the tube under tip deformation, which opens up an energy gap at the Fermi surface.