Quantum Transport Of Interface States In Monolayer And Bilayer Graphene

Graphene is a two-dimensional crystal with a hexagonal structure,which is made of carbon atoms.Since the graphene is successfully stripped from graphite materials at room temperature,it has attracted much attention and research.The graphene has the properties of a very high carrier mobility and low power,so it has become the most potential alternative to silicon.The tiny transistors made of graphene will be used for super-computer,and the processing speed of computer will be improved hundreds of times.In addition,as a result of the characteristics of high light transmittance and high strength for graphene,it will be the candidate material to manufacturing transparent electronics.Based on these superior properties and potential application value in graphene,it is necessary to explore the properties of graphene.In this paper,we first introduce the basic properties of graphene,the graphene nanoribbon,the preparation and application of graphene.Next,we introduce the theoretical models and methods used in the study of graphene.Finally,under the control of electric field and magnetic field,the quantum transport,the distribution of boundary states and the topological phase transition in the graphene nanoribbon are discussed in detail.Firstly,we study the quantum transport and the distribution of boundary states in gated zigzag-edged bilayer graphene under the boundary potential.Our results show that a variety of QVH phases can be induced by different boundary potentials,and that the spatial distribution of each edge state of the QVH phases can be individually controlled by manipulating the boundary potentials.We discuss the influence of impurities on graphene,finding that when the momentum separation between the valleys is large,the single-boundary QVH and QVH phases are protected from on-site nonmagnetic disorder or impurity scattering.On the contrary,when the momentum separation between the valleys is small,the unbalanced QVH phase can be destroyed even at a weak disorder.Secondly,we study the topological phase transition and the quantum transport under the tilted magnetic field in biased bilayer graphene.When the Zeeman effect is not considered,we find that the parallel component of the tilted magnetic field has no effect on band structure.On the other hand,when the zeeman effects are induced by strong magnetic field,both the vertical component and parallel component of the magnetic field can make the degeneracy of energy band lifted.Moreover,When the tilted magnetic field and the bias are the fixed values,the topological phase transition can be realized in graphene nanoribbon by adjusting the Fermi level,and different topological phase has different Hall conductivity.In conclusion,we explore the quantum transport,the distribution of boundary states and the topological phase transition in bilayer graphene under the electric field and magnetic field.These results are expected to be of reference to electronic devices.