Resonant coherent phonon spectroscopy of single-walled carbon nanotubes
Resonant coherent phonon spectroscopy of single-walled carbon nanotubes
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DOI：
10.1103/physrevb.79.205434
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发表时间：
2008-12
影响因子：
3.7
通讯作者：
G. D. Sanders;C. Stanton;J. Kim;K. Yee;Y. Lim;E. Hároz;L. Booshehri;J. Kono;R. Saito
中科院分区：
文献类型：
--
作者：
G. D. Sanders;C. Stanton;J. Kim;K. Yee;Y. Lim;E. Hároz;L. Booshehri;J. Kono;R. Saito
使用飞秒泵浦探针光谱与脉冲整形技术，人们可以在手性特定的半导体单壁碳纳米管中产生和检测相干声子。当泵浦光子能量与带间激子共振一致时，信号会共振增强，并且对此类数据的分析提供了关于光吸收、声子生成和声子引起的带结构调制的手性依赖性的丰富信息。为了解释我们的实验结果，我们使用电子态的紧束缚模型和声子的价力场模型开发了一种用于在单壁碳纳米管中产生和检测相干声子的微观理论。我们发现相干声子振幅满足驱动振荡器方程，其驱动项取决于光激发载流子密度。我们将理论结果与 $\text{mod}\text{ }2$ 纳米管的实验结果进行了比较，发现我们的模型在不同 $\text{mod}\text{ }2$ 族内部和之间的相干声子信号的相对强度方面提供了令人满意的总体趋势。我们还发现，与 $\text{mod}\text{ }2$ 纳米管相比，$\text{mod}\text{ }1$ 纳米管的相干声子强度要弱得多，这也与实验非常吻合。
Using femtosecond pump-probe spectroscopy with pulse-shaping techniques, one can generate and detect coherent phonons in chirality-specific semiconducting single-walled carbon nanotubes. The signals are resonantly enhanced when the pump photon energy coincides with an interband exciton resonance, and the analysis of such data provides a wealth of information on the chirality dependence of light absorption, phonon generation, and phonon-induced band-structure modulations. To explain our experimental results, we have developed a microscopic theory for the generation and detection of coherent phonons in single-walled carbon nanotubes using a tight-binding model for the electronic states and a valence force field model for the phonons. We find that the coherent phonon amplitudes satisfy a driven oscillator equation with the driving term depending on photoexcited carrier density. We compared our theoretical results with experimental results on $\text{mod}\text{ }2$ nanotubes and found that our model provides satisfactory overall trends in the relative strengths of the coherent phonon signal both within and between different $\text{mod}\text{ }2$ families. We also find that the coherent phonon intensities are considerably weaker in $\text{mod}\text{ }1$ nanotubes in comparison with $\text{mod}\text{ }2$ nanotubes, which is also in excellent agreement with experiment.