Resistance fluctuations in a low density 2D hole gas in GaAs

Abstract

We have measured the resistance fluctuations in 2D hole gases in GaAs quantum wells around the 2D “metal"-insulator transition (MIT) at temperatures between 35 and 700 mK. The magnitude of the noise spectrum has a l/$^\alpha ( \alpha = 1)$ frequency dependence and increases strongly as the density is lowered. There is a qualitative change in the temperature dependence at a density pg, higher than the 2D MIT critical density pc. Moreover, the noise magnitude shows a scaling behaviour as a function of the resistance, which can be attributed to a percolation transition, as suggested by theories which explain the resistivity vs. temperature dependence near the 2D MIT.