A theoretical model for the calculation of the phonon-drag thermopower,
Sg, in degenerately doped semiconducting single-wall carbon nanotubes
(SWCNTs) is proposed. Detailed calculations of Sg are performed as a
function of temperature, tube radius and position of the Fermi level. We derive
a simple analytical expression for Sg that can be utilized to determine
the free carrier density in doped nanotubes. At low temperatures Sg shows
an activated behavior characteristic of the one-dimensional (1D) character of
carriers. Screening effects are taken into account and it is found that they
dramatically reduce the magnitude of Sg. Our results are compared with
previous published experimental data in bulk p-doped SWCNT materials. Excellent
agreement is obtained in the temperature range 10-200 K for a consistent set of
parameters. This is a striking result in view of the complexity of these
systems.Comment: 21 pages, 6 figures. This version has been accepted for publication
in Phys. Rev.