arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0802.3203cond-mat.mes-hallcond-mat.mtrl-sci
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高度排列碳纳米管的磁谱:确定穿线磁通量的作用

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

J. Shaver, S. A. Crooker, J. A. Fagan, E. K. Hobbie, N. Ubrig, O. Portugall, V. Perebeinos, Ph. Avouris, J. Kono

摘要:

我们在低温(1.5 K)和高达55 T的强磁场($\textbf{\textit{B}}$)下,通过光学光谱研究了高取向单壁碳纳米管(SWCNTs)中的激子.拉伸SWCNT/聚丙烯酸膜,得到沿拉伸方向高度排列的SWCNT($\hat{n}$)。利用两个定义良好的测量几何形状,$\hat{n}\parallel\textbf{\textit{B}}$和$\hat{n}\perp\textbf{\textit{B}}$,我们提供明确的证据表明,光致发光的能量和强度只对平行于管轴的$\textbf{\textit{B}}$分量敏感。一维磁激子的理论模型,基于交换分裂的“亮”和“暗”激子带与Aharonov-Bohm相位相关的能量,质量和振子强度,成功地再现了我们的观察,并允许确定两个带之间的分裂为$\sim4.8$毫电子伏(6,5)单壁碳纳米管。

英文摘要:

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 ($\textbf{\textit{B}}$) 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, $\hat{n}\parallel\textbf{\textit{B}}$ and $\hat{n}\perp\textbf{\textit{B}}$, we provide unambiguous evidence that the photoluminescence energy and intensity are only sensitive to the $\textbf{\textit{B}}$-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 $\sim4.8$ meV for (6,5) SWCNTs.

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