Fine structure in the local chemical potential of a two-dimensional-electron system at filling factor ν=23

For investigating the compressible and incompressible strips in the depletion region near the edge of a two-dimensional electron system (2DES) in the integer and fractional quantum Hall regime at T<0.1 K, a metal single-electron transistor (SET) used as a local potential probe is directly fabricated on top of a GaAs/AlGaAs heterostructure containing the 2DES. A negative voltage applied to a sidegate electrode at 0.9 μm distance to the SET allows to shift the edge towards the SET island. Within the integer quantum Hall regime, due to charge fluctuations vs. time, strips of different screening properties are clearly resolved as a function of the sidegate voltage and the applied magnetic field — in agreement with previous results of Wei et al. (Phys. Rev. Lett. 81 (1998) 1674). Measurements reflecting the chemical potential variations of the 2DES vs. magnetic field show wiggles in the fractional quantum Hall regime around bulk filling factor View the MathML source, which still lack a good explanation.