Charge screening of single-walled carbon nanotubes in a uniform transverse electric field

The sp3 tight-binding model is used to calculate electronic structures of single-walled carbon nanotubes. The static dielectric function is evaluated from the random-phase approximation. strongly depends on the momentum (q) and angular momentum (L) transfer in the e e interactions. of L=1 at long wavelength limit represents the screening ability in the presence of a uniform transverse electric field. (q=0,L=1) mainly comes from the pπ electrons, but not the sp2σ electrons. The external field is greatly reduced. The dependence of (q=0,L=1) on the chiral angle, the nanotube radius, the magnetic flux, and the temperature is not strong. The transverse dielectric screening is largely enhanced by the increasing free carriers in conduction bands.