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 A. 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. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Excitons in carbon nanotubes / Maultzsch, J; Pomraenke, R; Reich, S; Chang, E; Prezzi, D; Ruini, Alice; Molinari, Elisa; Strano, Ms; Thomsen, C; Lienau, C.. - In: PHYSICA STATUS SOLIDI B-BASIC RESEARCH. - ISSN 0370-1972. - ELETTRONICO. - 243:13(2006), pp. 3204-3208. [10.1002/pssb.200669131]
Excitons in carbon nanotubes
RUINI, Alice;MOLINARI, Elisa;
2006
Abstract
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 A. 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. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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