Optoelectronic properties of silicon hexagonal nanotubes under an axial magnetic field

In this work, we derive a clear and easy-to-use analytic expression for optical transition matrix elements for the zigzag silicon hexagonal nanotubes (Si h-NTs) in the presence of axial magnetic field. The optical dipole matrix elements and optical absorption are analytically derived in terms of one-dimensional wave vector, kz and subband index l for a light polarization parallel to the tube axis. The model is based on a single-orbital π-electron tight-binding Hamiltonian extended up to the first nearest-neighbors. By comparing the band structure of tubes in different magnetic fields, one can see that the band gap is modified and the degenerated bands are split and create new allowed transition corresponding to the band modifications. Moreover, it is found that the system is metallic in the absence of magnetic field, but with increasing the magnetic flux the system tends towards the semiconducting behavior and the metal-semiconductor phase transition is observed.