Conductance Quantization In2D Topological Insulator With A Defect

Topological insulator is one of the most attractive areas in modern condense matterphysics. In this paper, with the help of the nonequilibrium Green’s function, we study thetransport properties of the two dimension (2D) topological insulator (HgTe quantum well).We calculated the conductance of HgTe quantum well with single defect or two defects inmagnetic field，in order to understand its changes in the transport by magnetic field anddefects. We mainly got the following conclusions:1. In magnetic field when HgTe quantum well join a square defects,the boundarystructure of HgTe quantum well will be broken.And there is a small gap between energybands. The conductance of the system fluctuates. When the defect area is greater than acertain value, system will arise0conductance platform,and increase with the area of thedefect.2. In magnetic field when HgTe quantum well join two square defects,coupling in thesystem will enchance. Electron scattering phenomenon will appear. Because electronic phasechanges, electrons arise interference phenomenon. And we can observe AB effect in thecurrent of spin up.It won’t appear in the current of spin down.