Which nanowire couples better electrically to a metal contact: armchair or zigzag nanotube?

The fundamental question of how chirality affects the electronic coupling of a nanotube to metal contacts is important for the application of nanotubes as nanowires. We show that metallic-zigzag nanotubes are superior to armchair nanotubes as nanowires, by modeling the metal-nanotube interface. More specifically, we show that as a function of coupling strength, the total electron transmission of armchair nanotubes increases and tends to be pinned close to unity for a metal with Fermi wave vector close to that of gold. In contrast, the total transmission of zigzag nanotubes increases to the maximum possible value of two. The origin of these effects lies in the details of the wave function, which is explained.