Formation Dirac point and the topological surface states for HgCdTe-QW and mixed 3D HgCdTe TI

Abstract

Abstract. In this paper the results of numerical calculations based on the finite difference method (FDM) for the 2D and 3D TI with and without uniaxial tensile strain for mixed Hg 1-x Cd x Te structures are presented. The numerical calculations were made using the 8x8 model for x from 0 up to 0.155 and for the wide range for the thickness from a few nm for 2D up to 150 nm for 3D TI as well as for different mismatch of the lattice constant and different barrier potential in the case of the QW. For the investigated region of the Cd composition (x value) the negative energy gap (E g =* 8 -* 6 ) in the Hg 1-x Cd x Te is smaller than in the case of pure HgTe which, as it turns out, has a significant influence on the topological surface states (TSS) and the position of the Dirac point for QW as well as for 3D TI. The results show that the strained gap and the position of the Dirac point against the * 8 is a function of the x-Cd compounds in the case of the 3D TI as well as the critical width of the mixed Hg 1-x Cd x Te QW.