Double valley Dirac fermions for 3D and 2D Hg1−xCdxTe with strong asymmetry

Abstract

In this paper the possibility to bring about the double-valley Dirac fermions in some quantum structures is predicted. These quantum structures are: strained 3D Hg1−xCdxTe topological insulator (TI) with strong interface inversion asymmetry and the asymmetric Hg1−xCdxTe double quantum wells (DQW). The numerical analysis of the dispersion relation for 3D TI Hg1−xCdxTe for the proper Cd (x)-content of the Hg1−xCdxTe compound clearly shows that the inversion symmetry breaking together with the unaxial tensile strain causes the splitting of each of the Dirac nodes (two belonging to two interfaces) into two in the proximity of the Γ-point. Similar effects can be obtained for asymmetric Hg1−xCdxTe DQW with the proper content of Cd and proper width of the quantum wells. The aim of this work is to explore the inversion symmetry breaking in 3D TI and 2D DQW mixed HgCdTe systems. It is shown that this symmetry breaking leads to the dependence of carriers energy on quasi-momentum similar to that of Weyl fermions.