Resonant Raman spectroscopy of deformed single-walled carbon nanotubes under both torsional and tensile strain

The first-order resonant Raman spectra of the deformed single-walled carbon nanotubes (SWCNTs), suffered from both tensile and torsional strains, have been studied within the nonorthogonal tight-binding model. It is found that: (1) two kinds of the strains almost do not change the frequencies of the low-energy Raman modes. In contrast, the tensile strain downshifts all the G -band Raman modes, but the torsional strain-induced G -band shifts depend on the tube's chirality and the mode symmetry. (2) The changes in resonant Raman intensity depend on the strain type, mode symmetry, and the selected electronic transition energy. For example, the torsional strain increases (decreases) the TO (LO) mode intensity, and the tensile strain has little effect on that of the TO mode but increases or decreases the LO mode intensity, depending on the electronic transition energy. (3) More importantly, when both the tensile and torsional strains are simultaneously applied to the SWCNTs, there would be an interference effect between two kinds of strains on the strain-induced frequency shifts and intensity changes, which are not equal to a simple sum over those induced separately by tensile and torsional strains, and the interference effect is found to depend on the tube chirality and mode symmetry, which has already been partially supported by the experimental observations.