### Abstract

We report an experimental investigation of the fractional quantum Hall effect (FQHE) at the even-denominator Landau-level filling factor ν=1/2 in very-high-quality wide GaAs quantum wells and at very high magnetic fields up to 45 T. The quasi-two-dimensional electron systems we study are confined to GaAs quantum wells with widths W ranging from 41 to 96 nm and have variable densities in the range of â‰4×1011 to â‰4×1010 cm^{-}2. We present several experimental phase diagrams for the stability of the ν=1/2 FQHE in these quantum wells. In general, for a given W, the 1/2 FQHE is stable in a limited range of intermediate densities where it has a bilayerlike charge distribution; it makes a transition to a compressible phase at low densities and to an insulating phase at high densities. The densities at which the ν=1/2 FQHE is stable are larger for narrower quantum wells. Moreover, even a slight charge distribution asymmetry destabilizes the ν=1/2 FQHE and turns the electron system into a compressible state. We also present a plot of the symmetric-to-antisymmetric subband separation (Δ_{SAS}),which characterizes the interlayer tunneling, vs density for various W. This plot reveals that Δ_{SAS} at the boundary between the compressible and FQHE phases increases linearly with density for all the samples. There is no theoretical explanation for such a simple dependence. Finally, we summarize the experimental data in a diagram that takes into account the relative strengths of the interlayer and intralayer Coulomb interactions and Δ_{SAS}. We conclude that consistent with the conclusions of some of the previous studies, the ν=1/2 FQHE observed in wide GaAs quantum wells with symmetric charge distribution is stabilized by a delicate balance between the interlayer and intralayer interactions and is very likely described by a two-component (Ψ_{331}) state.

Original language | English (US) |
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Article number | 245413 |

Journal | Physical Review B - Condensed Matter and Materials Physics |

Volume | 88 |

Issue number | 24 |

DOIs | |

State | Published - Dec 11 2013 |

### All Science Journal Classification (ASJC) codes

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics

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## Cite this

*Physical Review B - Condensed Matter and Materials Physics*,

*88*(24), [245413]. https://doi.org/10.1103/PhysRevB.88.245413