Effects of strain and defects on the electron conductance of metallic carbon nanotubes

Strain dependence of electronic structure and transport properties of (6,0) carbon nanotubes has been thoroughly studied using first-principles calculations in conjunction with Green's function techniques. We have found that the quantum conductance is very sensitive to structural deformation and relaxation. The conductance decreases monotonically with increasing strain, for both compression and elongation. In an elongated tube, strain-induced electron localization is the dominating mechanism that controls the contribution of molecular orbitals to conductance. Transport properties are also drastically affected by the presence of defects. Our results have demonstrated that the electronic transport properties of a nanoscale device are closely related to the nature of the band structure of the metallic lead, the details of chemical bonding in the scattering region, and the interaction between Bloch states and the molecular orbitals.