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

Topological insulators (TI) based on InAs/GaSb quantum wells are appealing due to their rich phase diagram with a topological and normal insulating phase. Due to the spatial separation of electrons and holes in the InAs and GaSb layer, respectively, a switching between both phases can be achieved by external electric fields using a top and back gate. We present another tuning knob using optical excitation. By monitoring the charge carrier densities, we can identify the hybridized band structure and in-plane magnetic field measurements evidence the TI gap. We will discuss how the interplay of negative photoconductivity and persistent charge carrier buildup leads to the tuning of the phase diagram by optical excitation.