Fractional Quantization of the Hall Effect

Magnetotransport of two-dimensional electrons and holes was studied in magnetic fields up to 300 kG and temperatures down to 0.5 K. In addition to previously reported structures at Landau-level filling factors ν=1/3 and 2/3, new structures were resolved at ν=4/3, 5/3, 2/5, 3/5, 4/5, and 2/7. The results suggest that fractional quantization of the Hall effect exists in multiple series, each based on the inverse of an odd integer.