Quantum Hall effect and insulating state near the charge neutrality point in an InAs/GaSb quantum well*

We present transport measurements in a gated InAs/GaSb double quantum well (QW) sandwiched between two AlSb barriers. In this system a QW for electrons in InAs and a QW for holes in GaSb coexist next to each other and a hybridization gap is expected to occur. We can tune the transport from electrons to the holes by applying a top gate voltage. In presence of a perpendicular magnetic field, we observe well defined quantum Hall plateaus in both sides. Interestingly, at the charge neutrality point a strong increase in the longitudinal resistivity is observed with increasing perpendicular magnetic field, accompanied by the onset of a non-local resistance of similar magnitude. The co-existence of these two effects is described by a model of counter-propagating and dissipative quantum Hall edge channels, shorted by a residual bulk conductivity.\\[4pt] Reference: Fabrizio Nichele \textit{et al}., arXiv:1308.3128 (2013). Christophe Charpentier \textit{et al}., \textit{Appl. Phys. Lett.} 103, 112102 (2013).