Finite size effects on the quantum spin Hall state in HgTe quantum wells under two different types of boundary conditions*
Cheng Zhi, Chen Rui, Zhou Bin†
       
Schemes of the strip samples of two-dimensional TI under two different types of boundary conditions simulated by a tight-binding lattice. (a) The symmetric geometry: a TI strip is sandwiched between two NI strips with the same material parameters; (b) the asymmetric geometry: one side of the TI strip is a TI/NI interface, and the other side is a vacuum/TI interface. The TI region is a strip of an inverted HgTe QW with finite width L , and the NI region with width W is HgTe QW with a normal electronic band structure. In the text, the mass parameter M in the TI region is taken as −10 meV, and in NI it is 10 meV. The lattice constant of the tight-binding model is a (= 2 nm).