Morphing of 2D Hole Systems at ν=3/2 in Parallel Magnetic Fields: Compressible, Stripe, and Fractional Quantum Hall Phases

A transport study of two-dimensional (2D) holes confined to wide GaAs quantum wells provides a glimpse of a subtle competition between different many-body phases at Landau level filling $\nu=3/2$ in tilted magnetic fields. At large tilt angles ($\theta$), an anisotropic, stripe (or nematic) phase replaces the isotropic compressible Fermi sea at $\nu=3/2$ if the quantum well has a symmetric charge distribution. When the charge distribution is made asymmetric, instead of the stripe phase, an even-denominator fractional quantum state appears at $\nu=3/2$ in a range of large $\theta$, and reverts back to a compressible state at even higher $\theta$. We attribute this remarkable evolution to the significant mixing of the excited and ground-state Landau levels of 2D hole systems in tilted fields.