Unperturbed Optical Transition Energies in Carbon Nanotubes

Abstract Submitted to the

Unperturbed Optical Transition Energies in Carbon Nanotubes

Yan Yin1, Stephen Cronin2, Andrew Walsh1, Alexander Stolyarov2, Michael Tinkham2, Anthony Vamivakas3, Wolfgang Bacsa3,4, M. Selim Ünlü3,1, Bennett B Goldberg1,3 and Anna K. Swan3,

1Physics department, Boston University, Boston, MA 02215,
Contact e-mail: swan@bu.edu

We have measured the resonance Raman excitation profiles on individual and isolated semiconducting single wall carbon nanotubes suspended in air. We find that the previously measured ES22 optical transitions from nanotubes in surfactants are blue shifted 70-90 meV with respects to our measurements of nanotubes in air, despite the larger surrounding dielectric constant in solution. This surprising result implies that the energy contribution from exciton binding is larger than from band-gap renormalization, in contradiction to current theoretical understanding, which predicts that the Coulomb driven exchange interaction gives rise to a large increase of the band gap energy counteracted by a somewhat smaller exciton binding energy shift (1,2).

1. T. Ando, J. Phys. Soc. Jpn., 66, 1066 (1997).

2. H. Sakai, H. Suzuura and T. Ando J. Phys. Soc. Jpn., 72, 1698 (1997).

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