Quantum Transport Properties Of Graphene Nanoribbons Controlled By External Field

Graphene,is a two-dimensional Dirac material and has the linear dispersion in the vicinity of zero enery,therefore,it has unusual electronic properties.Firstly,we introduce the preparation method of graphene,the structure and charaeter-istics of graphene,and the application prospects of graphene.Then,the theoretical model and method are explored,especially focusing on the tight-binding model of graphene nanoribbons under different external conditions.Secondly,we study the energy band structure of graphene nanoribbons with differ-ent boundaries under stress and AB sublattice potential,respectively.When the stress is applied on armchair graphene nanoribbons,it has an influence on its electronic structure,where as the electronic structure of is almost unaffected by stress.However,when we con-sider the AB sublattice potential,whether it is armchair or zigzag graphene nanoribbons,the band gap is increase.Finally,we investigate the effect of uniaxial tensile stress in the electronic struc-ture and transport properties of hexagon lattice via a tight-binding approach.When the magnetic field is zero,the stress has a significant effect on the Dirac point of the two-dimensional hexagonal material.We find that two Dirac points merge into a single point to generate a semi-Dirac cone as the tensile stress increases.The semi-Dirac cone is anisotropy with linear and parabolic dispersions at distinct directions.For a larger tensile stress,a band gap can be opened which indicates a phase transition from metallic phase to insulator phase.In the presence of magnetic field,we discuss the relationship between the energy level and the magnetic field.The Landau levels split into two branches under appropriate tensile stress,resulting in interesting Hall conductance,We expect these find-ings to be valuable for electronic devices.