Spin transition of a two-dimensional hole system in the fractional quantum Hall effect

The effect of the complex valence-band Landau-level (LL) structure on the fractional quantum Hall (FQH) effect of a two-dimensional hole system has been studied in a modulation-doped quantum well (QW) with front and back gates. Owing to the spin-orbit interaction and the band mixing in the valence band, changing the potential asymmetry of the QW with the front and back gates allows us to vary the LL structure for a fixed hole density. We observed a remarkable transition in the ν=4/3 FQH effect with a striking resemblance to the spin transitions observed for tilted-field experiments. Self-consistent effective-mass calculations were carried out to confirm that the transition is driven by the change in the effective Zeeman energy.