Screening at doped nanotube junctions beyond linear response

Screening length at doped nanotube junctions, which is of primary importance in device applications, has been a controversial issue. Employing a fully self-consistent tight-binding approach, we show that, for both sharp and smooth external potential drops, the screening length is of the order of a few carbon-ring separations. This rather strong screening of the Coulomb interaction is accompanied by the oscillation of transferred charge at the junction, and is observed for both semiconducting and metallic tubes despite minor differences.