Electronic excitations in coupled armchair carbon nanotubes

We study the low-frequency electronic excitations in two-dimensional armchair carbon nanotube superlattices. The characteristics of the electronic structures and the superlattice geometry are directly reflected in the electronic excitations. The excitation properties, the dielectric function, the excitation spectrum, and the plasmon frequency, strongly depend on the direction and the magnitude of the transferred momentum, and the nanotube radius. There are low-frequency plasmons except that the transferred momentum is perpendicular to the tubular axis. They belong to acoustic plasmons.