Quantum Dynamics Of Electron In Quasi-one-dimensional Nanostucture Systems

Electronic properties of quasi-one-dimension nanostructure systems have been widely studied in recent years. In order to understand the unusual elctronic transport in nanomaterial, the study of quantum diffusion in quasi-one-dimensional systems has attracted considerable interest. In this thesis, we present a systematical numerical investigation of quantum diffusion in quasi-one-dimension nanostructured systems in terms of the autocorrelation function C(t) and the mean square displace ment d(t).The thesis consists of five chapters. Chapter 1 is the introduction of the thesis, It involves the preparation, theory background and the studying signification of quasi-one-dimension nanomaterial. In Chapter 2 involves the fundamental theory of quantum diffusion and Runger-Kutta method.Chapter 3 concerns the quantum diffusion in one-dimensional periodic nanowire and edge ordered nanowire. We show that the dynamic behavior of electron is ballistic in periodic nanowire system, and there exists a transition from ballistic to localized behavior with the disorder strength increasing, similar to that in two-dimensional quasiperiodic systems. For a given disorder, the ballistic-nonballistic transition is also obtained with the nanowire width increasing, exhibiting a typical quantum size effect.The quantum dynamics of the single-walled carbon nanotubes is studied in Chaper 4. It involves the effect of tube-diameter, chirality and the disorder on the dynamic behavior of electron in the single-walled carbon nanotubes. The results show that there exists a transition from ballistic to nonballistic behavior with the disorder strength increasing. Interesting, the disorder and defect have the different influence on the electronic transport in the nanotubes with various tube-diameter and/or chirality. For the larger tube-diameter nanotube, the disorder and defect have less influence on the electronic transport than in nanotube with smaller tube-diameter. For the nanotube with various chirality, the influence on the electronic transport in zigzag nanotube is stronger than in armchair nanotube.Considered both the finite size and the edge disorder, we explore in chaper 5 the dynamic behavior of electron in graphene nanoribbons (GNRs) with various geometries, based on quantum diffusion theory. It is shown that in the regime of stronger disorder, the decay exponentδand the diffusion exponentβincrease with the edge disorder increasing, while they decrease in the regime of weaker disorder. A localization-quasidelocalization transition can be observed in GNRs upon varying the strength of edge disorder, similar to that in a shell-doped nanowire. Also, it is found that the edge disorder has the influence of varying importance on the electronic transport in GNRs, which depends on its width and edge geometry. In addition, a singular quantum size effect may exist in such an edge disordered GNRs. The results can contribute towards understanding of the strange transport properties of graphene sheets and their potential applications.