Single-molecular physics of single-walled nanotubes encapsulating magnetic metals

我们利用激光烧蚀法合成了高质量的单壁碳纳米管，并揭示了它们有趣的性质，如下所示：1.我们首次利用高纯度的单壁碳纳米管，通过光电子能谱证实了一维货车霍韦奇异性。此外，我们还发现了电子态密度（DOS）的两个幂律依赖关系。第一个是束缚态密度与结合能的幂律关系，第二个是费米能级上的束缚态密度与温度的幂律关系。该指数分别为0.46和0.48，这与一维金属系统（即Tomonaga Luttinger液体（TLL）系统）的理论预测相一致。我们的研究结果是TLL系统在单壁碳纳米管束中实现的最可靠的证据。2.采用乙醇化学气相沉积法制备了镶嵌在支撑材料中的孤立碳纳米管，并对其光学性质进行了测量。样品显示出非常窄的径向呼吸拉曼峰，其半宽度小于1.5 cm-1。拉曼光谱不包含任何特殊的束峰。这一新的样品为我们提供了有关碳纳米管电子结构和光跃迁选择规则的有用信息。3.当我们将水分子引入碳纳米管中时，我们发现水分子在低温下转变为冰纳米管。通过改变碳纳米管的直径可以控制冰纳米管的直径。我们发现不同直径的冰纳米管具有不同的凝固点。冰纳米管的直径越大，其凝固点越低，这与经验规律相反。4.我们合成了单壁碳纳米管包裹金属富勒烯，并进行了光谱测量。双壁碳纳米管的形成也通过X射线衍射和拉曼光谱进行了研究。

We have synthesized high-quality single-wall carbon nanotubes by the laser ablation methods and revealed interesting natures of them as listed below.1.We have first confirmed one-dimensional van Hove singularities by means of photoemission spectroscopy by using highly purified single-wall carbon nanotubes. Furthermore, we have fond two power law dependences of electronic density of states (DOS). The first one is power law dependence of DOS on the binding energy and the second one is power law of DOS at the Fermi level on the temperature. The exponents are 0.46 and 0.48, respectively that just agree with the theoretical predictions for the one-dimensional metallic system so called Tomonaga Luttinger liquid (TLL) system. Our result is the most reliable evidence that the TLL system is realized even in the bundle of single-wall carbon nanotubes.2.The isolated nanotubes embedded in the support materials were synthesized by chemical vapor deposition of ethanol and the optical properties of them were measured. The sample shows very narrow radial breathing Raman peaks with the half width less than 1.5 cm-1. The Raman spectrum does not contain any peaks peculiar to the bundles. This new sample gave us useful information about electronic structure of carbon nanotubes and the selection rule of the optical transition.3.When we introduced water molecules into carbon nanotubes, we found that water molecules transformed to ice-nanotubes at low temperature. By changing the diameter of carbon nanotubes we can control the diameter of ice-nanotube. We found that ice nanotube with different diameter has different freezing point. The larger diameter of ice-nanotube leads to the lower freezing point, which is opposite to the empirical rule.4.We have synthesized single-wall carbon nanotubes encapsulating metallo-fullerenes and have done some spectroscopic measurements. Double wall carbon nanotube formation was also investigated by X-ray diffraction and Raman spectroscopy.