Coexistence of Topological and Normal Insulating Phases in Electro-Optically Tuned InAs/GaSb Bilayer Quantum Wells

We report on the coexistence of both normal and topological insulating phasesin InAs/GaSb bilayer quantum well induced by the built-in electric field tunedoptically and electrically. The emergence of topological and normal insulatingphases is assessed based on the evolution of the charge carrier densities, theresistivity dependence of the gap via in-plane magnetic fields and the thermalactivation of carriers. For the Hall bar device tuned optically, we observe thefingerprints associated with the presence of only the topological insulatingphase. For another Hall bar processed identically but with an additional topgate, the coexistence of normal and topological insulating phases is found byelectrical tuning. Our finding paves the way for utilizing a newelectro-optical tuning scheme to manipulate InAs/GaSb bilayer quantum wells toobtain trivial-topological insulating interfaces in the bulk rather than at thephysical edge of the device.