Doping Effect on Magnetism and Transport Property of Heterojunction between Carbon and Boron Nitride Nanotubes

First-principles study on the electronic structures and electron-transport properties of one-dimensional heterostructured carbon/boron nitride nanotubes is carried out. It is found that p-type atom substitutional doping, in which, e.g., one N atom is replaced with one C atom at the zigzag carbon nanotube edge, takes an electron from the energetically flat states below the Fermi level, which results in the spin-polarized ground-state electronic structure. On the other hand, n-type doping leads to the nonmagnetic ground-state electronic structure because of the strong sigma-pi hybridization in the smaller-diameter nanotube while the spin polarization is realized in the larger-diameter nanotube. More interestingly, in contrast to undoped nanotubes, where the edge states do not conduct electrons owing to the symmetry mismatch with the conducting carbon nanotube states, the fluctuation of the symmetry due to the presence of the doped atom can realize the spin-dependent resonant tunneling through the edge states. Our results indicate that the substituted atom plays important roles for the transport through the edge states as well as the spin-polarized electronic structure.