Edge effects in an insulating state of an electron-hole system in magneticfield

We find that an InAs/GaSb based electron-hole system exhibits insulating be haviour when the numbers of occupied electron and hole Landau levels are eq ual. In this insulating state, the Hall resistance becomes symmetric under field reversal, and both the Hall and longitudinal resistances display repr oducible fluctuations. We propose a simple model based on edge states to ac count for these properties, and show that a comparison to the conductivity measured from a Corbino disc is consistent with the model. (C) 2001 Elsevie r Science B.V. All rights reserved.