Electric field effects on spin transport in
graphene nanoribbons and metallic carbon nanotubes
Young-Woo Son /
Dept of Physics, Konkuk Univ. Seoul, Korea
Based on first-principles calculations, we investigate the effects of electric
fields on the magnetic properties of graphene nanoribbons (GNRs) [1,2] and defective
metallic single-wall carbon nanotubes (SWNTs) [3]. First, a half-metallicity
is predicted in GNRs if the in-plane homogeneous electric fields are applied across
the zigzag shaped edges of the systems [4]. Such asymmetric electronic structures
for each spin originate from the fact that the spatially separated spin polarized
states with opposite spin orientations in the semiconducting GNRs are shifted oppositely
in energy by the applied fields. This closed the gap associated with one
spin orientation and widens the other. Second, we show that vacancies or carbon
adatoms in (10,10) SWNTs play a role of quasi-localized magnetic impurities and that
their relative energy levels with respect to the Fermi energy are changed by the applied
transverse electric fields [3,5]. So, the resulting spin-polarized conductances
in the systems are shown to be tunable. For some impurities, the orientation of the
majority spin electrons in conducting channels at the Fermi energy can be switched
to the opposite spin by an experimentally attainable electric field. Our results
suggest that pure organic nanomagnets or perfect spin polarizations could be realized
in carbon nanostructures and their spin transport properties are controllable
by transverse electric fields.
[1]
[2]
[3]
[4]
[5]
Y.-W. Son, M. L. Cohen, S. G. Louie, Phys. Rev. Lett. 97, 216803 (2006).
L. Yang, C. H. Park, Y.-W. Son, M. L. Cohen, S. G. Louie, Phys. Rev. Lett. in press (2007).
Y.-W. Son, M. L. Cohen, S. G. Louie, Nano Lett. in press (2007).
Y.-W. Son, M. L. Cohen, S. G. Louie, Nature 444, 347 (2006).
Y.-W. Son, J. Ihm, M. L. Cohen, S. G. Louie, H. J. Choi, Phys. Rev. Lett. 95, 216602
(2005).