Fractional quantum Hall effect in a two-dimensional hole system

We have studied the fractional quantization of the Hall resistance at 0.51 K in two-dimensional hole systems formed at p⁺:Ga_1-xAlₓAs-GaAs interfaces with mobilities as high as 8.0 ×{} 10⁴ cm²/Vs at 4 K. In addition to the Hall quantization for a fractional filling factor ν=2/3, we report for the first time the observation of an almost fully developed Hall plateau at ν=3/5 and the existence of weak but distinct structure in the magnetoresistance for ν=3/7 and 6/5. Similarly, magnetoresistance minima occurred at ν=5/3, 4/3, 2/3, 3/5, and 2/5. In contrast with two-dimensional electron systems, conspicuously absent was any magnetoresistance feature in the vicinity of ν=4/5.