Exciton states in metallic zigzag single-walled carbon nanotubes under uniaxial strain

• Excitons states was studied under uniaxial strain in the metallic carbon nanotubes.
• M11- and M22- excitons increase with increasing the uniaxial strain.
• M11+ and M22+ excitons decrease with the uniaxial strain increasing.
• Splitting of M11M11 and M22M22 will disappear as the uniaxial strain increase up to some degree.
• Excitons that nearest to Fermi level increase with increasing uniaxial strain.

The exciton energy spectrum and its binding energy under the uniaxial strain have been theoretically studied by using the tight-binding model in the metallic zigzag single-walled carbon nanotubes (SWNTs). It is found that the energy of M11- and M22- excitons and their binding energies increase with the increase of uniaxial strain, but the energy of M11+ and M22+ excitons and their binding energies decrease as the uniaxial strain increase. So, we can deduce that the splitting of M11M11 and M22M22 exciton will disappear as the uniaxial strain increases up to some degree, which is expected to be detected by the future experiment. On the other hand, it is interesting to calculate the exciton energy spectrum and binding energies of the bands that nearest to the Fermi level, with a narrow gap under the uniaxial strain. The obtained results show that they increase with increasing the uniaxial strain, based on which a supplemented tool is offered to detect the deformation degree of a metallic SWNT under uniaxial strain. In addition, we expect the results obtained here can offer some useful information for the future THz applications.