Electrons in Carbon Nanotubes: The Spin feels the Spiral
Carbon nanotubes are typically viewed as long, thin, one dimensional conductors, but at the nanoscale they are actually tiny tubes. Electrons can spiral around the circumference tube in a clockwise or counter-clockwise fashion as they move up and down its length, creating an orbital magnetic moment. Previously, this orbital motion was taken to be decoupled from the electron’s intrinsic spin, meaning that the direction that the spin points is not affected by the sense (clockwise or counter-clockwise) of the spiralling motion. CNS investigators have recently demonstrated that, in truth, the spin and orbital motion of electrons are coupled. The coupling favours parallel alignment of the orbital and spin magnetic moments for electrons. These measurements, though initially surprising, are consistent with recent theories that predict spin-orbit coupling due to the nanotube’s cylindrical structure. These findings have important implications for applications of nanotubes in spintronics and quantum computing.
Schematic of two electrons in a carbon nanotube, showing the spin (in green) and the orbital motion (in pink.) The energy is lower when the spin and orbital moments are aligned, as for the rightmost electron.
[Lead CNS Investigators: Ralph, McEuen - C-Nanoelectronics Thrust, Center for Nanoscale Systems, Cornell University]
For additional information see:
F. Kuemmeth, S. Ilani, D.C. Ralph, and P.L. McEuen, “Coupling of Spin and Orbital Motion of Eelectrons in Carbon Nanotubes,” Nature 452, 448 (2008).