Fractional quantum Hall effect in high-mobility two-dimensional hole gases in tilted magnetic fields

The fractional quantum Hall effect (FQHE) has been studied as a function of magnetic field in a series of high-quality p-type GaAs-${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterojunctions. The magnetic-field dependence of the ν=4/3 FQHE state, investigated by tilting the samples in the applied field, is consistent with a change in the spin polarization of the ground state. The behavior suggests that the Zeeman splitting of the interacting carriers forming this ground state is larger in this material, at a given magnetic field, than in comparable n-type samples. At high tilt angles, structure is observed to emerge in the second Landau level at ν=8/3.