Non-Linear transport in low density 2D hole systems

We report measurements of non-linear magnetotransport in 10 nm wide p-doped GaAs/Al_0.1Ga_0.9As quantum wells with low hole density (n ~ 10¹⁰ cm^-2) and high mobility (m ≈ 5 x 10⁵ cm²/Vs). The Quantum Hall plateau-to-plateau transitions exhibit a universal dependence on bias voltage. We compare the results to theoretical predictions by assuming that the narrowing of the plateaus is caused by the temperature rise in the sample caused by the Joule heating. We find a good qualitative agreement with the predictions, but, surprisingly, the data show a stronger dependence on bias in the zero-bias limit than the theory suggests. We also discuss the high-frequency rectification spectroscopy as an approach for exploring dynamic effects in low-density hole systems and, in particular, the physics of insulating phases in two-dimensional transport at low carrier densities.