Electric-Field Driven Topological Phase Transition in InAs/InGaSb Composite Quantum Wells

Band-inverted InAs/(In,Ga)Sb composite quantum wells (CQWs) have been under intensive study as a 2D topological insulator. Among other 2D topological insulators, the CQW hosts an electrically tunable band alignment thanks to its double layer structure wherein electron and hole gases are spatially separated. This work presents electric-field-driven topological-to-normal insulator transition for recently-developed strained InAs/In_xGa_1-xSb CQWs [1, 2] with a large hybridization gap up to 35 meV. By measuring the energy gap as a function of electric field, we observed gap closing and reopening as expected for a topological phase transition. [1] T. Akiho et al., Appl. Phys. Lett. 109, 192105 (2016). [2] L. Du et al., Phys. Rev. Lett. 119, 056803 (2017).