A metal-semiconductor-metal transform appeared in the metallic single-walled carbon nanotubes, controlled by the combined effect of magnetic field and uniaxial strain

Abstract

As known to us, the metallic zigzag tubes will open a band gap by applying the magnetic field or uniaxial strain. The exciton states of the nearest band to Fermi level (M00) in the metallic carbon nanotubes are calculated by a tight-binding model, under the combined effect of the magnetic field and uniaxial strain. It is found that the excitation energy and binding energy of the metallic zigzag carbon nanotube (24, 0) have the similar variation tendency, which are split into M00+ and M00− excitons by the applied magnetic field and strain. When the uniaxial strain is applied, for M00+, it increases with increasing magnetic field, while for M00−, it decreases. However, it is interesting to find that as the magnetic field increases, the M00− exciton will decrease to be zero and a metal-semiconductor-metal change will appear, which is expected to be confirmed by experiments. The obtained result provides some useful information for future THz applications by controlling the magnetic field and uniaxial strain.