We observe fractional quantum Hall effect (FQHE) at the even-denominator Landau level filling factor ν=1/2 in two-dimensional hole systems confined to GaAs quantum wells of width 30 to 50 nm and having bilayer-like charge distributions. The ν=1/2 FQHE is stable when the charge distribution is symmetric and only in a range of intermediate densities, qualitatively similar to what is seen in two-dimensional electron systems confined to approximately twice wider GaAs quantum wells. Despite the complexity of the hole Landau level structure, originating from the coexistence and mixing of the heavy- and light-hole states, we find the hole ν=1/2 FQHE to be consistent with a two-component, Halperin-Laughlin (Ψ331) state.
@article{arxiv.1401.7605,
title = {Fractional Quantum Hall Effect at $\nu=1/2$ in Hole Systems Confined to GaAs Quantum Wells},
author = {Yang Liu and A. L. Graninger and S. Hasdemir and M. Shayegan and L. N. Pfeiffer and K. W. West and K. W. Baldwin and R. Winkler},
journal= {arXiv preprint arXiv:1401.7605},
year = {2014}
}