Magneto-spectroscopy of Highly-Aligned Carbon Nanotubes: Identifying the Role of Threading Magnetic Flux

Abstract

We have investigated excitons in highly-aligned single-walled carbon nanotubes (SWCNTs) through optical spectroscopy at low temperature (1.5 K) and high magnetic fields ($\text{B}$) up to 55 T. SWCNT/polyacrylic acid films were stretched, giving SWCNTs that are highly aligned along the direction of stretch ($\hat{n}$). Utilizing two well-defined measurement geometries, $\hat{n}\parallel \text{B}$ and $\hat{n}\perp \text{B}$, we provide unambiguous evidence that the photoluminescence energy and intensity are only sensitive to the $\text{B}$-component parallel to the tube axis. A theoretical model of one-dimensional magneto-excitons, based on exchange-split `bright' and `dark' exciton bands with Aharonov-Bohm-phase-dependent energies, masses, and oscillator strengths, successfully reproduces our observations and allows determination of the splitting between the two bands as $\sim 4.8$ meV for (6,5) SWCNTs.

arXiv comment4 pages, 4 figures

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• Exciton Lifetime Paradoxically Enhanced by Dissipation and Decoherence - Toward Efficient Energy Conversion of Solar Cell
• Magneto-reflection spectroscopy of monolayer transition-metal dichalcogenide semiconductors in pulsed magnetic fields