Half-metallic finite zigzag single-walled carbon nanotubes from first principles

Abstract

Density-functional calculations predict half-metallicity in zigzag single-walled carbon nanotubes of finite \nlength with the two ends saturated with hydrogen. We have analyzed the change of the β- and α-spin electronic \ngaps under the influence of an electric field applied along the nanotube axis. The half-metallic behavior, in \nwhich the electronic gap is zero for one spin flavor and nonzero for the other, is obtained for a critical electric \nfield of 3.0/w V/Å, where w is the length of the nanotube. This critical field is the same as that predicted for \ngraphene nanoribbons. By a detailed analysis of the spin structure of the ground state, we show the relevance \nof the edge states, electronic states spatially localized at the carbon atoms of the nanotube boundaries, on the \non-set of half-metallicity, and on the magnetic properties of the finite semiconducting zigzag nanotubes.