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Quantum Hall effect near the charge neutrality point in a two-dimensional electron-hole system.

Research paper by G M GM Gusev, E B EB Olshanetsky, Z D ZD Kvon, N N NN Mikhailov, S A SA Dvoretsky, J C JC Portal

Indexed on: 21 May '10Published on: 21 May '10Published in: Physical review letters



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.