Transport Property Of Weyl Semimetal-Superconductor System

In this paper,the transport properties of Weyl semimetal(WSM)-superconductor system are studied by means of non-equilibrium Green’s function technique.The model we proposed is a two-terminal system,which is magnetic Weyl semimetal connected by superconductor.We mainly calculate the coefficient of Andreev reflection in the system.Then we study the influence of edge states on Andreev reflection.We investigate the coefficient of Andreev reflection in two-dimension case and in three-dimension case.The results show that Andreev reflection occurs in both cases.When the incident electrons move in the Z direction,there are only the incident electrons of the bulk states participating in the Andreev reflection of the system in this case.The reason is that the electrons in the WSM topological edge states have no speed in the Z direction.As the Fermi energy increasing,the density of state increases,and the bulk states becomes more involved in Andreev reflection which leads to the enhancement of Andreev reflection.When the incident electrons move in the Y direction,the direction of the electrons in the WSM edge states and the incident electrons are the same.That is to say,both the topological edge states and the bulk states participate in the Andreev reflection of the system.The anisotropy of the WSM in the Y and Z directions leads to the different intensity of the Andreev reflection when the incident electrons move in the Y and Z directions.Then we study the influence of WSM topological edge states on Andreev reflection.The results show that the topological edge states have great influence on Andreev reflection of the system.When the WSM topological edge states disappear,Andreev reflection is suppressed.With the increasing of Fermi energy,the bulk states of WSM gradually occupy the dominant position of Andreev reflection,while the contribution of WSM edge states gradually decrease.