Electronic excitations of double-walled armchair carbon nanotubes

The low-frequency electronic excitations in double-walled armchair carbon nanotubes are studied within the random-phase approximation. The intertube atomic overlaps significantly affect the low-energy bands and thus enrich the low-frequency single-particle excitations and collective excitations. They induce more plasmon modes, reduce the plasmon strength, and change acoustic plasmons into optical plasmons. The predicted results could be verified by the electron-energy-loss spectroscopy.