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Proceedings Paper

Photoexcitation of the triplet exciton in single wall carbon nanotubes
Author(s): Bruce W. Alphenaar; Aditya D. Mohite; Jagadeesh S. Moodera; Tiffany S. Santos
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Paper Abstract

The carbon nanotube photoexcitation spectrum is dominated by excitonic transitions, rather than interband transitions between continuum states. There are eight distinct excitonic transitions (four singlet and four triplet), each with two-fold degeneracy. Because the triplet excitons are spin polarized with electron and hole spins both pointing in the same direction, they are optically inactive, and optical spectroscopy has revealed no evidence for their existence. Here, we show that by the interaction with a spin filter ferromagnetic semiconductor, photoexcitation of the carbon nanotube triplet exciton is possible, and its contribution to the photocurrent can be detected. The perturbation provided by the spin filter allows for inter-system mixing between the singlet and triplet excitonic states, and relaxes the spin selection rules. This supplies the first evidence for the existence of the triplet exciton, and provides an avenue for the optical excitation of spin polarized carriers in carbon nanotubes.

Paper Details

Date Published: 20 August 2009
PDF: 9 pages
Proc. SPIE 7396, Physical Chemistry of Interfaces and Nanomaterials VIII, 739607 (20 August 2009); doi: 10.1117/12.827254
Show Author Affiliations
Bruce W. Alphenaar, Univ. of Louisville (United States)
Aditya D. Mohite, Univ. of Louisville (United States)
Jagadeesh S. Moodera, Massachusetts Institute of Technology (United States)
Tiffany S. Santos, Massachusetts Institute of Technology (United States)

Published in SPIE Proceedings Vol. 7396:
Physical Chemistry of Interfaces and Nanomaterials VIII
Oliver L. A. Monti; Oleg V. Prezhdo, Editor(s)

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