Optical absorption of zigzag single walled boron nitride nanotubes

In a realistic three-dimensional model, optical matrix element and linear optical absorption of zigzag single walled boron nitride nanotubes (BNNTs) in the tight binding approximation are studied. In terms of absolute value of dipole matrix elements of the first three direct transitions at kz=0, we divided the zigzag BNNTs into three groups and investigated their optical absorption spectrum in energy ranges E<5,77.5eV. We found that in lower energies, E<5eV, all groups show different behaviors while in the higher energies, 77.5eV, their behaviors depend on their even or odd nanotube index. We also found that in the energy range 7