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Topology and Transport in Carbon Nanotubes

碳纳米管的拓扑和传输

基本信息

批准号：
08640412
负责人：
ANDO Tsuneya
金额：
$ 1.34万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

A carbon nanotube consists of coaxially rolled graphite sheets. Because the distance between different sheets is much larger than the nearest neighbor carbon atoms, electronic properties are dominated by those of a single-shell nanotube. A single-shell CN can be either a metal or a semiconductor depending on the circumference length and the helical fashion. The purpose of this project is to study effects of the topological structure of nanotubes on their transport properties.Various calculations have been performed to predict energy bands of nanotubes. It has been found that the characteristic properties are all reproduced quite well in a k・p method, which is effective in the study of effects of external fields such as a magnetic and electric field. In fact, it has been successful in the study of magnetic properties including the Aharonov-Bohm effect on the band gap, optical absorption spectra, and lattice instabilities in the presence and absence of a magnetic field.Transport properties are interesting because CN's have a structure topologically different from that of conventional quantum wires fabricated using semiconductor heterostructures. There have been some reports on experimental study of transport in CN bundles. Quite recently, measurements of magnetotransport of a single nanotube became possible.During the period of two-year project, the conductivity of CN's was calculated using the Boltzmann transport equation and in Landauer' approach for a model of short-range scatterers. The study was made on transport across a junction of nanotubes having difference circumferences and on exciton effects in optical absorption spectra of semiconducting nanotubes and metallic nanotubes in the presence of an Aharonov-Bohm magnetic flux.

碳纳米管由同轴轧制的石墨片组成。由于不同片层之间的距离比最近邻的碳原子大得多，电子性质由单壳纳米管的电子性质决定。根据圆周长度和螺旋方式，单壳CN可以是金属或半导体。本项目的目的是研究纳米管的拓扑结构对其输运性质的影响。人们已经进行了各种计算来预测纳米管的能带。结果表明，k·p方法能很好地再现这些特征性质，是研究磁场和电场等外场效应的有效方法。事实上，它已经成功地研究了磁性，包括Aharonov-Bohm效应对带隙的影响，光吸收光谱，以及有无磁场下的晶格不稳定性。输运性质很有趣，因为CN的结构在拓扑上不同于传统的用半导体异质结制备的量子线。已有一些关于CN丛中输运的实验研究的报道。最近，单根纳米管的磁输运测量成为可能。在两年的项目期间，用玻尔兹曼输运方程和朗道方法计算了碳纳米管的电导率，并采用了短程散射体模型。研究了在Aharonov-Bohm磁通存在下，半导体纳米管和金属纳米管在光学吸收光谱中的输运和激子效应。