Electron transport in a toroidal carbon nanotube device

Taking the curvature and disorder into account, the electron transport in a carbon molecular device consisting of a toroidal carbon nanotube connected with two semi-infinite metallic carbon nanotubes, has been investigated by using the tight-binding Green's function method and the Landauer-Büttiker formula. It is shown that the current through the device can be modulated by the disorder in the molecular device and/or the torus-tube distance. The negative differential conductance is obtained at relatively large bias, while the current has little increase for small voltages. The results are in good agreement with the experimental observation.