Unconventional Hall effect near charge neutrality point in a   two-dimensional electron-hole system
  The transport properties of the two-dimensional system in HgTe-based quantum wells containing simultaneously electrons and holes of low densities are examined. The Hall resistance, as a function of perpendicular magnetic field, reveals an unconventional behavior, different from the classical N-shaped dependence typical for bipolar systems with electron-hole asymmetry. The quantum features of magnetotransport are explained by means of numerical calculation of the Landau level spectrum based on the Kane Hamiltonian. The origin of the quantum Hall plateau {\sigma}xy = 0 near the charge neutrality point is attributed to special features of Landau quantization in our system. 
O. E. Raichev, G. M. Gusev, E. B. Olshanetsky, Z. D. Kvon, N. N.   Mikhailov, S. A. Dvoretsky, and J. C. Portal
cond-mat.mes-hall