Pseudo-spin filter in metallic single-walled carbon nanotubes

We analyze the scattering properties of low-energy electrons in metallic single-walled carbon nanotubes in the presence of structural defects. In particular, we focus on vacancy defects characterized by the lack of two carbon atoms. We show how the geometry of the defect with respect to the tube symmetry establishes the available scattering channels. Furthermore, we show how the reconstruction of the chemical bond among the carbon atoms at the place of the defect can induce a selection rule based on the pseudo-spin of the scattered electrons. This selection rule results in an effective filtering of the scattered electrons with respect to the pseudo-spin.