title: Quantum Hall effect near the charge neutrality point in a two-dimensional electron-hole system.
abstract: We study the transport properties of HgTe-based quantum wells containing simultaneously electrons and holes in a magnetic field B. At the charge neutrality point (CNP) with nearly equal electron and hole densities, the resistance is found to increase very strongly with B while the Hall resistivity turns to zero. This behavior results in a wide plateau in the Hall conductivity sigma(xy) approximately = 0 and in a minimum of diagonal conductivity sigma(xx) at nu = nu(p) - nu(n) = 0, where nu(n) and nu(p) are the electron and hole Landau level filling factors. We suggest that the transport at the CNP point is determined by electron-hole "snake states" propagating along the nu = 0 lines. Our observations are qualitatively similar to the quantum Hall effect in graphene as well as to the transport in a random magnetic field with a zero mean value.
authors.affiliation: Instituto de Física da Universidade de São Paulo, 135960-170, São Paulo, SP, Brazil.
authors.forename: G M
authors.initials: GM
authors.lastname: Gusev
authors.forename: E B
authors.initials: EB
authors.lastname: Olshanetsky
authors.forename: Z D
authors.initials: ZD
authors.lastname: Kvon
authors.forename: N N
authors.initials: NN
authors.lastname: Mikhailov
authors.forename: S A
authors.initials: SA
authors.lastname: Dvoretsky
authors.forename: J C
authors.initials: JC
authors.lastname: Portal