Large Thermospin Effects in Carbon Nanotubes with Vacancy Defects

Abstract

We systematically investigated the possibility of improving thermospin effects in single-walled carbon nanotubes (SWCNTs) by vacancy engineering. The proposed method possesses several advantages: (I) both the armchair and zigzag SWCNTs with vacancy defects exhibit a spin-semiconducting phase with a localized band structure near the Fermi level; (II) applying a thermal gradient can generate spin-up and spin-down currents with the same magnitudes but opposite directions, demonstrating the existence of a pure spin current without any applied bias; (III) a giant spin Seebeck coefficient SS, comparable with those of other carbon-based structures, can be achieved; (IV) the phononic thermal conductance in defective SWCNTs is reduced by about 50%, thus strongly enhancing the thermospin conversion efficiency ZST; and (V) varying the nanotube diameter can tune the spin gap, such that the spin gap increases as the nanotube becomes narrower, indicating the possible application of SWCNTs in thermospintronic.