Magneto collective excitations of armchair carbon nanotubes

Magneto single-particle and collective excitations of armchair carbon nanotubes are studied within the RPA. They strongly depend on the angular momentum (L), the momentum (q), and the magnitude (φ) and the direction (α) of magnetic field. The L=0 mode has lower excitation frequencies, higher excitation intensity, stronger q-dependence, and smaller critical momentum, as compared with the L=1 mode. The plasmon frequency of L=0 mode increases (decreases) with φ(α), while the strength exhibits the opposite behavior.