Direct Observation of Dark Excitons in Individual Carbon Nanotubes: Role of Local Environments

A. Srivastava; H. Htoon; V. I. Klimov; J. Kono

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arXiv · 0804.0875

Direct Observation of Dark Excitons in Individual Carbon Nanotubes: Role of Local Environments

A. Srivastava·H. Htoon·V. I. Klimov·J. Kono

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Abstract

We report the direct observation of the spin-singlet dark excitonic state in individual single-walled carbon nanotubes through low-temperature micro-photoluminescence spectroscopy in magnetic fields. A magnetic field up to 5 T, applied along the nanotube axis, brightened the dark state, leading to the emergence of a new emission peak. The peak rapidly grew in intensity with increasing field at the expense of the originally-dominant bright exciton peak and finally became dominant at fields $>$3 T. This behavior, universally observed for more than 50 nanotubes of different chiralities, can be quantitatively explained through a model incorporating the Aharonov-Bohm effect and intervalley Coulomb mixing, unambiguously proving the existence of dark excitons. The directly measured dark-bright splitting values were 1-4 meV for tube diameters 1.0-1.3 nm. Scatter in the splitting value emphasizes the role of the local environment surrounding a nanotube in determining the excitonic fine structure of single-walled carbon nanotubes.

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A. Srivastava, H. Htoon, V. I. Klimov, J. Kono. 2008-04-05. Direct Observation of Dark Excitons in Individual Carbon Nanotubes: Role of Local Environments. https://arxiv.org/abs/0804.0875

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