Gordeev Georgy, Wasserroth Sören, Li Han, Flavel Benjamin, Reich Stephanie
Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
Nano Lett. 2021 Aug 25;21(16):6732-6739. doi: 10.1021/acs.nanolett.1c00295. Epub 2021 Aug 9.
Moiré patterns are additional, long-range periodicities in twisted crystalline bilayers. They are known to fundamentally change the electronic states of the layers, but similar effects on their mechanical and vibrational properties have not been discussed so far. Here we show that the moiré potential shifts the radial breathing mode in double-walled carbon nanotubes (DWCNTs). The change in frequency is expected to be proportional to the shift in optical transition energies, which are induced by the moiré patterns. To verify our model, we performed resonance Raman scattering on purified and sorted semiconducting DWCNTs. We find that the radial breathing mode shifts up to 14 cm higher in energy followed by displacement of optical transition energies of up to 200 meV to lower energies, in comparison to the single-walled tubes. We show how to identify the strong coupling condition in DWCNTs from their phonon frequencies and construct a Kataura plot to aid their future experimental assignment.
莫尔条纹是扭曲晶体双层中额外的长程周期性结构。已知它们会从根本上改变层的电子态，但迄今为止尚未讨论过对其机械和振动性质的类似影响。在此我们表明，莫尔势使双壁碳纳米管（DWCNT）中的径向呼吸模式发生了位移。频率变化预计与由莫尔条纹引起的光学跃迁能量的位移成正比。为了验证我们的模型，我们对纯化和分类后的半导体DWCNT进行了共振拉曼散射。我们发现，与单壁管相比，径向呼吸模式的能量向上移动高达14厘米，同时光学跃迁能量最多向下移动200毫电子伏特。我们展示了如何从DWCNT的声子频率识别强耦合条件，并构建了一个片仓图以辅助其未来的实验归属。
