Ballistic transport in bent-shaped carbon nanotubes

We report theoretical investigations of ballistic quantum transport properties of smoothly bent semiconducting single-walled carbon nanotubes (SWCNTs). The SWCNT is doped into NxN and PxP forms where N and P stand for N-type and P-type doping, x takes N-type, P-type or intrinsic I-type. Our calculation is based on a state-of-the-art non-equilibrium Green's function approach combined with density functional theory. The smooth bent induces a small electron redistribution on the SWCNT arc, which leads to rich and major transport differences between the NxN and PxP tubes. Conductance G of NNN tubes does not change with the bending angle β, while G of PPP tubes decreases with it. G of NPN and PNP tubes increases with β, while that of the PNP tubes varies with it in an oscillatory manner. The bent induced transport phenomena can be well understood by analyzing the microscopic physics of the electronic density distribution and quantum interferences between scattering states which traverse different paths along the bent-shaped tubes. The predicted conductance versus bent angle is useful for estimating how a flexible system may behave when strained and/or bent.