The Influence Of The In-Plane Electric Field On The Transport Properties Of Silicene Nanoribbons

Graphene is formed by a single layer of carbon atoms, which is a honeycomb-like two-dimensional nano-material. It is the first widely recognized two-dimensional material. It has many unique physical properties because of its special structure, which aroused people's wide attention. Both the silicon and carbon are belong to the fourth main-group elements, the silicon in theory can form one that similar to graphene's honeycomb-like two-dimensional lattice structure. With the gradual deepening of the study and the successfully achieved of silicene, it is found that silecene has a variety of novel physical properties. These features are of great significance for future industrial applications as well as basic physics research. The silicon element and modern semiconductor industry are of well convergence properties, so more and more attention is drawn to the study of silicene.In the first chapter, we have mainly introduced the cause of silicene to arouse people's study interest and referred the research history and current situation of it. At the same time, we have introduced the application prospective of it, and the change and influence it brings to human beings living in the future. Finally, we have introduced the structure characteristics of silicene, the characteristics of its electronic transport, which make readers form a preliminary understanding for silicene.In the second chapter, we have mainly introduced the Green's function method in the transport theory of the mesoscopic system, especially the recursive green's function technique and the derived the Green function of the system. As long as we know the Green's function for the whole system, we can calculate the system's conductance.In the third chapter, we have mainly studied the transport properties of the system when the electric field is applied. In the vertical electric field, the edge state of the nanoribbon was destroyed, and an energy gap of 2|?SO-Vz| was opened when the electric field intensity was larger than the strength of the effective intrinsic spin-orbit coupling. In the in-plane electric field, the edge state of the nanoribbon is robust whether the electric field intensity was larger than the strength of the effective intrinsic spin-orbit coupling or not. But the Dirac point of the system appeared a shift of Vy/2, and the shift direction changed with the direction of the electric field. Because the vertical electric field and the in-plane electric field can destroy the structural inversion symmetry of the system, the valleys are spin-polarized, and the direction of the spin polarization in the valley could be adjusted by the electric field. The vertical electric field and the electric field in the plane can be applied with different intensity and directions. It is found that the system could follow the shift law of the Dirac point in the in-plane electric field, while the spin orientation of the valley is more inclined to obey the distribution law of the vertical electric field. When both of the electric field intensities are larger than the strength of the effective intrinsic spin-orbit coupling, the system energy band appears a gap closed phenomenon. Through studying the effect of disorder on the transport properties of the system, the phase transition from a topological insulator to an insulator is not found when the vertical electric field intensity was less than the strength of effective intrinsic spin-orbit coupling. The in-plane electric field does not destroy the edge state of the system, and a well-performing conductance platform of 2e2/h is still maintained under the strong disorder scattering. When the strength of the vertical electric and in-plane electric field are larger than the effective intrinsic spin-orbit coupling, the vertical electric field would open an energy gap, while the energy gap became increasingly smaller until reclosed with the in-plane electric field increasing. In the presence of the disorder scattering, the conductance platform2e2/h is destroyed, and the edge state of the system is destroyed. It is shown that the phase transition of a common insulator to a topological insulator does not appear and the system is not the quantum spin Hall system.