Morphing of two-dimensional hole systems at v=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 a Landau level filling v = 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 v = 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.