Excitons in carbon nanotubes

• Published in: Physica Status Solidi (b) 2006-11, Vol.243 (13), p.3204-3208
• Main Authors: Maultzsch, J., Pomraenke, R., Reich, S., Chang, E., Prezzi, D., Ruini, A., Molinari, E., Strano, M. S., Thomsen, C., Lienau, C.
• Format: Article
• Language: English
• Subjects: 71.15.Qe; 73.22.−f; 78.20.Bh; 78.67.Ch; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals; Exact sciences and technology; Nanotubes; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200669131

We present two‐photon excitation luminescence experiments on carbon nanotubes which show the excitonic origin of the optical excitations. The two‐photon allowed exciton state, which has even parity under rotation about the U‐axis, is roughly 300 meV above the one‐photon active, odd‐parity state. This indicates exciton binding energies on the order of 400 meV for nanotubes with diameters around 8 Å. Ab‐initio calculations of the exciton wavefunctions and energies are in good agreement with our experimental results, confirming the predictions on the symmetry of the exciton states. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)