In quantum Hall effect experiments, there is a critical measuring current, beyond which dissipation becomes apparent. Using samples with a narrow constriction in the middle, we have observed critical current densities which are much higher than previously reported values.

We measured the current-dependent asymmetry of spin-split Shubnikov-de Haas [SdH! peaks at a variety of GaAsIGaAIAs heterojunctions with various sample geometries. The different current dependence of the spin-split SdH peaks is due to a spin-dependent equilibration between edge and bulk states described by an equilibration length 7. . The onset of the equilibration above a certain current limit marks the transition from non-local to partially local transport. The 1 values and the onset currents of the spin levels were investigated for different channel widths and temperatures. Measurements in tilted magnetic fields gave evidence for the dependence of the asymmetry of the spin-split SdH peaks on the relation between Landau and Zeeman splitting.

No abstract

The currentand temperaturedependent broadening of the resistivity peaks in the region between adjacent quantum Hall plateaus is measured in two different GaAs/AI,Ga,-,As samples. Power law behaviour is found for temperature dependent effective electron temperature can be extracted. We find T. -p with a current heating exponent a 0.5.

No abstract