Conductance spectra of metallic carbon nanotube bundles from first principles

We report a first-principles analysis of electronic transport characteristics for n,n carbon nanotube bundles. When n is not a multiple of 3, intertube coupling causes universal conductance suppression near Fermi level regardless of the rotational arrangement of individual tubes. However, when n is a multiple of 3, the bundles exhibit a diversified conductance dependence on the orientation details of the constituent tubes. The total energy of the bundle is also sensitive to the orientation arrangement only when n is a multiple of 3. All the transport properties and band structures can be well understood from the symmetry consideration of whether the rotational symmetry of the individual tubes is commensurate with that of the bundle. This finding may shed some light on understanding and applications of nanotube bundle interconnect technology. Single walled carbon nantubes SWNTs can form a bundle with a triangular cross-sectional lattice in a selforganized manner, a good example of hierarchical solids. The number of SWNTs in a bundle ranges from a few to hundreds. It has been known that close-packed bundles containing parallel individual nanotubes possess superb mechanic, 1 thermal, 2 and electronic 3‐5 properties. Since nanotube bundles are ubiquitous in nanotube synthesis reaction, they have attracted great attention both experimentally and theoretically. Very recently it was determined that the minimal bundling number is between 3 and 8 in vertically aligned SWNT films. 6 For these bundles containing small number of tubes, the one-dimensional 1D properties of SWNT can still be attainable. This is in contrast to bundles with large number of tubes where bulk properties might