Recently, there is a growing interest in the InAs/GaSb composite quantum well sandwiched between two AlSb barriers because of its unique band alignment. In this hybrid system an electron layer in InAs can coexist with a hole layer in the GaSb and a hybridization gap is expected to occur due to quantum tunnelling between the layers. Depending on the QWs’ thicknesses and on the perpendicular electric field, a rich phase diagram is predicted. It should be possible to electrically tune the sample from standard conducting phases to insulating, semimetallic, or topological insulator phases.

In this poster, I will present transport measurements in a Hall bar device where it was possible to observe both electron and hole transport by tuning a top gate voltage. At high magnetic field we observe well defined quantum Hall plateaus for both electron and holes, indicating the good quality of the sample. Surprisingly, at the charge neutrality point we observe that the longitudinal resistivity increases to much higher than the resistance quantum, together with a strong non-local resistance of similar magnitude. We explain our observation with a model which includes the existence of counter propagating dissipative edge channels coupled with residual bulk scattering. Finally I will show our recent measurements on the mesoscopic devices, where we observe signature of ballistic transport, boundary scattering and discuss how the fabrication process influences the electronic transport in these devices.

References:

1. Fabrizio Nichele, Atindra Nath Pal, Patrick Pietsch, Thomas Ihn, Klaus Ensslin, Christophe Charpentier, Werner Wegscheider Phys. Rev. Lett., 112, 036802 (2014).
2. Charpentier et al. Appl. Phys. Lett. 103, 112102 (2013).
3. Susanne Mueller, Atindra Nath Pal, Matija Karalic, Thomas Tschirky, Christophe Charpentier, Werner Wegscheider, Klaus Ensslin, Thomas Ihn, Phys. Rev. B (R) 92, 081303 (2015).