The electrical transport properties of a bipolar InAs/GaSb system have been studied in a magnetic field. The resistivity oscillates between insulating and metallic behavior while the quantum Hall effect shows a digital character oscillating from 0 to 1 conductance quantum e2/h. The insulating behavior is attributed to the formation of a total energy gap in the system. A novel looped edge state picture is proposed associated with the appearance of a voltage between Hall probes which is symmetric on magnetic field reversal.
Nicholas, R. J., Takashina, K., Lakrimi, M., Kardynal, B., Khym, S., Mason, N. J., Symons, D. M., Maude, D. K., & Portal, J. C. (2000). Metal-insulator oscillations in a two-dimensional electron-hole system. Physical Review Letters, 85(11), 2364-2367. https://doi.org/10.1103/PhysRevLett.85.2364