Spin Filter Circuit Design Based on a Finite Single-Walled Carbon Nanotube of the Zigzag Type

A complete circuit, consisting of a zigzag-edge single-walled carbon nanotube (zSWCNT) as a gate with attached transacetylene chains anchoring 2-mercaptopyridine residues as conducting junctions and gold clusters as electrodes, is investigated by density functional theory, with both plane-wave and atom-centered Gaussian bases. Spin polarization is found to be preserved in zSWCNTs upon covalent grafting of the conducting substituents, and spin conductivity is observed through the entire circuit. These findings are relatively insensitive to the zSWCNT diameter and the gold cluster size. This suggests that the present design may be an interesting candidate for a nanotube-based spin filter prototype.