Coexistence of topological and normal insulating phases in electro-optically tuned InAs/GaSb bilayer quantum wells

Topological insulators (TIs) based on InAs/GaSb bilayer quantum wells are appealing due to the electric field tuning between topological and normal insulating (NI) phases. Here, the authors report on the coexistence of NI and TI phases in electro-optically tuned InAs/GaSb bilayer quantum wells and helical edge channels in the bulk of the sample. These findings pave the way to the manipulation and utilization of helical edge channels by using spatially defined gates (optically or electrically), separating them from the physical edges.