Scanning SQUID measurements of current flow in InAs/GaSb Quantum Wells

InAs/GaSb quantum wells have been predicted theoretically to exhibit the quantum spin hall phase in the inverted regime. In this phase, spin-polarized helical edge modes are expected to exist. Previous published results on length and width dependence of InAs/GaSb 4-terminal devices suggests these helical edge states coexist with a residual bulk conductivity when the device is tuned into the minigap. We probe the spatial distribution of currents in devices using a scanning SQUID to measure the resulting magnetic fields. Specifically, we find that when the device is tuned into the gap with a front gate, current flows along the edge and coexists with bulk current. We also look at dependence on back gate voltage and temperature dependence.