| Since the discovery of Weyl semimetals,they have been popular among researchers because of their unique dispersion relations.Researchers have verified the existence of Weyl semimetals from theoretical predictions and experiments,respectively,which laid the foundation for studying the transport problems associated with Weyl semimetals.The study of superconducting heterojunctions associated with Weyl semimetals was initiated to investigate their transport properties.It was found that the scattering properties of normal metal-superconductor（NS）heterojunctions based on type-II of Weyl semimetals change as the tilt angle increases by tilting the NS heterojunction by a certain angle.However,there are relatively few studies on changing the tilt angle of normal metal-superconductor-normal metal（NSN）heterojunctions,and our work is to change the tilt angle of NSN heterojunctions and observe the scattering properties of the system.In this thesis,the scattering properties of NSN junctions of a type-II of Weyl semimetals are theoretically investigated by using the scattering matrix method after tilting the system at a certain angle.The calculation results show that the tilt angle can determine the scattering mechanism of the system.When the tilt angle is small,there are two types of local Andreev reflection and two types of electron tunneling in the NSN junction,including radial Andreev reflection,specular Andreev reflection,radial electron tunneling and specular electron tunneling.With the increase of the tilt angle,the local Andreev reflection is gradually suppressed,and when the tilt angle exceeds the critical angle,the transport process in the NSN junction is the same as that in the NSN junction of normal metal,and electron normal reflection,electron tunneling,local Andreev reflection and cross Andreev reflection will occur simultaneously.Then,based on this model,the total conductance of the system,the conductance of two-electron tunneling and the conductance of crossed Andreev reflection are also calculated with bias,chemical potential and tilt angle under zero-bias and non-zerobias conditions.The calculated results show that the total conductance of the zero-bias system is not affected by the chemical potential and is not affected by the incident angle when the tilt angle is less than the critical angle,while it decreases with the increase of the incident angle when the tilt angle is larger than the critical angle,while the conductance of the non-zero-bias cross-Andreev reflection is enhanced with the enhancement of the incident angle under certain conditions.In this thesis,the influence of the NSN junction tilt angle on the scattering mechanism and the variation law of the scattering coefficient and partial differential conductance under the influence of different factors are investigated,which are important for the study of low-dimensional quantum transport problems and provide the theoretical basis for the design of new electronic devices in the future. |
