Band gap of two-dimensional topological insulator with a double quantum well structure

The bulk energy gap of two-dimensional (2D) topological insulators (TIs) is generally small, leading to their study being limited to extremely low temperatures, thus increasing the energy gap of 2D TIs is an urgent challenge. It has been reported that the compressive strain could enhance the band gap of the 2D TI to about 55 meV. Based on this result, this paper further calculated the band structures of 2D TIs with a special structure, i.e., the double quantum well, and especially evaluated their band gaps. We found that by choosing different internal barrier thicknesses, asymmetry factors and electric fields, numerical results show that the energy gap of the TIs with double quantum well (DQW) structure can further reach over 70 meV. This result might be significant for the possible applications of 2D TIs.