Length-dependent transport properties of (12,0)/(n,m)/(12,0) single-wall carbon nanotube heterostructures -: art. no. 075438

We study the length-dependent transport behaviors of (12,0)/(n,m)/(12,0) heterostructures using a pi-orbital tight-binding model and a Green's function technique. When (n,m) is a semiconducting tube, or a (6,6) tube with sixfold rotational symmetry C-6 on the interfaces, conductance G decreases exponentially with the length L of the (n,m) tube. However, we find an anomalous increase of G with L in the (12,0)/(9,0)/(12,0) heterostructure. We explain this anomalous phenomenon and reproduce the transport behaviors of the heterostructure very well by introducing an exponentially dropped potential (EDP) around the interfaces. This model helps us to understand the physics of carbon nanotubes with finite lengths.