Study On Quantum Transport Characteristics In ?-T₃ Model

The discovery of graphene promotes the comprehensive study of two-dimensional Dirac materials.The band structure is composed of two Dirac cones,and the two cone vertices intersect.We call it the band structure with pseudospin of 1/2.The3 T lattice or the dice lattice is a very popular two-dimensional Dirac material in recent years.Its band structure is similar to that of graphene,except that at the intersection of the vertices of the Dirac cone,a flat band is sandwiched,band structure with pseudospin of1/2.There is now a new two-dimensional material?-T₃ model that links graphene to the3 T lattice by the parameter ?.In previous studies,it was found that Klein tunneling occurs when particles are incident normal to the barrier;super-Klein tunneling occurs when the particles take some fixed energy.Based on the above-mentioned strange physical phenomena occurring in the?-T₃ model,we apply electric and magnetic fields to the model to study the corresponding transport properties.The specific content is as follows:In chapter one,the main content is the introduction of some materials,band structures and main properties related to the?-T₃ model such as graphene,Klein tunneling and Dirac-Weyl system with pseudospin S=1.In chapter two,the related concepts and theories used in the study of transport properties of ?-T₃ model are introduced,including quantum tunneling effect,scattering matrix theory,conductance and shot noise in mesoscopic quantum devices.In chapter three,The transport properties of the?-T₃ model after an applied electric field are mainly studied.Through the relevant formula derivation and numerical calculation,we obtain the schematic diagrams of transmittance,conductance,shot noise and Fano factor with various parameters.We know that when no electric field is applied,the Klein tunneling effect occurs under certain conditions.However,after the applied electric field,a gap is formed between the Dirac cones of the band structure,and the position of the flat strip is at the bottom of the conduction band.In this case,the Klein tunneling effect does not occur regardless of the model coefficient ?,the energy gap size?,the incident particle energyFE,and the incident angle incident.This also shows that the applied electric field will have an impact on the barrier transport of the?-T₃ model.In chapter four,The transport properties of the?-T₃ model after an applied magnetic field are mainly studied.Similarly,the relevant formula derivation and numerical calculations are then plotted to analyze the changes in transmittance,conductance,shot noise,and Fano factor.When a magnetic field is applied,the flat strip in the band structure is in the middle of the energy gap.In this case,the particles can also undergo a Klein tunneling effect in a specific case.This also shows that the position of the flat belt has a great influence on the barrier tunneling.In chapter five,It mainly summarizes the current research and looks forward to the future development prospects.