The quantum Hall effect in electron-hole hybridized systems is examined using back-gated InAs/(AlSb)/GaSb heterostructures with different electron-hole coupling. When the electrons and holes are strongly coupled, it is found that quantized Hall states appear when the net filling factor [νnet=(n-p)h/eB, where n and p are the electron and hole densities, respectively] is an integer, and that it is not a necessary condition for independent electron and hole filling factors (νe=nh/eB and νh=ph/eB) to be integers simultaneously. The observed phenomena can be interpreted in terms of a simple model where the Landau-level fans associated with the electrons and holes hybridize resulting in an effective band gap at νnet=0, and the quantized Hall states occur according to the number of hybridized Landau levels occupied above this gap.
Suzuki, K., Takashina, K., Miyashita, S., & Hirayama, Y. (2004). Landau level hybridization and the quantum Hall effect in InAs/(AlSb)/GaSb electron-hole systems. Physical Review Letters, 93(1), . https://doi.org/10.1103/PhysRevLett.93.016803