FRACTIONAL HALL QUANTIZATION OF TWO-DIMENSIONAL HOLES IN GaAs-GaAlAs HETEROSTRUCTURES.

The quantum Hall effect in two-dimensional electron systems has been reported in a number of heterostructures, in which the Hall resistance, rho //x//y equals h/ nu e**2, shows plateaus at integral values of nu and the magnetoresistance, rho //x//x, tends to vanish simultaneously. We report a study of the fractional quantum Hall effect in the GaAs-GaAlAs hole system by use of different carrier concentrations. A series of fractional values were observed: nu equals 2/5, 3/5, 2/3, 6/5, 4/3, and 5/3. These values were identified from both rho //x//y and rho //x//x for nu less than 1 but only from rho //x//x for nu greater than 1 which usually occurred at relatively low fields. Compared to electrons, the features at 3/5 and 6/5 were rather prominent while that at 6n 51 4/5 was conspicuously absent. In the low-field region, the oscillatory characteristics in rho //x//x were complex, reflecting the complicated valence band structure. 10 refs.