Physical Properties Of Carbon Nanotube Ring

Nanometer-scale materials have drawn a surge of interests due to their tremendous potential technical applications in miniaturization of electronic devices. As an ideal electromagnetic element, the carbon nanotube ring (CNTR) has attracted much interest ever since its discovery. In this thesis, some reasonable models of carbon nanotube ring (CNTR) have been built by taking into account the curvature, hybridization, and disorder. The electronic structure, electronic transport, magnetic properties as well as thermal properties of carbon nanotube ring (CNTR) have been studied systematically via developing effective methods. It mainly contains the following six chapters:In the first chapter, we give a brief introduction for the research background and the potential applications of CNTR, as well as the problems which will be solved in this thesis.In chapter two, based on the singleπorbital tight-binding approximation, the dependence of electronic structure of armchair CNTR on the radii of ring and tube is investigated by using the wave function decomposition method, in which the curvature effect is fully taken into account. It is shown that the electronic structure is similar to that of cluster (quantum dot) for these rings with small radius, while with increasing the ring's radius, the energy spectrum transition is observed from discrete to continuous ones.In chapter three, based on the four orbital tight-binding approach, the effects of hybridization, disorder, and the external fields (electromagnetic field) on the electronic structure of CNTR are studied. It is demonstrated that the curvature induced hybridization has a pronounced effect on its electronic structure. For different type of CNTR, the dependence of energy gap on the number of unit cells (ring's radius) exhibits different oscillatory characteristics. A phase transition from semiconductor to insulator can be induced by strong disorder strength. The effect of external fields is also discussed at the end of this chapter. It is found that the external fields have dramatic influence on its electronic structure, including the variation for the degeneration of energy levels, metal-semiconductor-metal transition and so on. In the presence of an external voltage, the electron transport properties of CNTR is investigated in chapter four by using the tight-binding Green's function. The correlation between the current-voltage characteristic and the disorder strength as...