Bistability in the current-induced breakdown of the quantum Hall effect

The structure of the longitudinal resistance in the breakdown behaviour of the quantum Hall effect (QHE) of GaAs/AlGaAs heterostructures is studied at a temperature of about 100 mK using samples with a constricted current path. Time-resolved measurements on a sample with a 50 mu m wide constriction show that the current-induced breakdown of the QHE evolves as a switching between at least two states, a non-dissipative one and a resistive one. The two states may coexist in some region of magnetic field and sample current. This shows up in the time behaviour of the longitudinal voltage, which is time-distributed in a statistical manner. Increasing the sample current at fixed magnetic field increases the time the current carriers stay in the resistive state rho dis until at high enough currents all backswitching into the non-dissipative state is suppressed. At filling factors nu or=2 the sample shows no similar effect. The results are discussed within the framework of several existing models for the breakdown behaviour of the QHE.

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