Observation of the i=1/2 fractional quantum Hall plateau in AlGaAs/GaAs/AlGaAs selectively doped double heterostructures

Abstract

An inverted and a normal GaAs/AlGaAs interface grown back to back in a socially selectively doped double heterostructure (SDDH) has been studied in magnetic fields up to 12 T and at temperatures down to 0.3 K. The longitudinal resistance goes to zero at the minima of the Shubnikov-de Haas oscillations. The Hall resistivity is found to exhibit the quantum Hall effect. By etching the surface of the double heterostructure wafer the authors create an imbalance in the density of electrons in the two parallel two-dimensional electronic sheets. Although in this way they create only a modest change in the electron densities, they observe a significant change in the Shubnikov-de Haas oscillations, which can be interpreted as a beat between the oscillations of two electron layers with different densities. At the same time they observe a significant variation of the width of the quantum Hall steps. The most astonishing feature of the results is a clear quantum Hall plateau at 1/2 filling in each of the two parallel layers observed at temperatures below 1 K and at a magnetic field about 10 T. Weak localisation was also studied and such experiments are consistent with two parallel and independent two-dimensional electronic layers.