The long-standing problem of inexplicably short spin relaxation in carbon nanotubes is examined. The curvature-mediated spin-orbital interaction is shown to induce fluctuating electron spin precession causing efficient relaxation in a manner analogous to the Dyakonov-Perel mechanism. Our calculations in single-walled semiconducting nanotubes estimate longitudinal (spin-flip) and transversal (decoherence) relaxation times as short as 150 and 130 ps at room temperature along with a pronounced anisotropic dependence. Interference of electrons originating from different valleys can lead to even faster dephasing. The results can help clarify the measured data, resolving discrepancies in the literature.

• Received 30 July 2010

DOI:https://doi.org/10.1103/PhysRevB.82.155449