Size dependence- and induced transformations- of fractional quantum Hall effects under tilted magnetic fields.

Two-dimensional electron systems subjected to high transverse magnetic fields can exhibit Fractional Quantum Hall Effects (FQHE). In the GaAs/AlGaAs 2D electron system, a double degeneracy of Landau levels due to electron-spin, is removed by a small Zeeman spin splitting, [Formula: see text], comparable to the correlation energy. Then, a change of the Zeeman splitting relative to the correlation energy can lead to a re-ordering between spin polarized, partially polarized, and unpolarized many body ground states at a constant filling factor. We show here that tuning the spin energy can produce fractionally quantized Hall effect transitions that include both a change in [Formula: see text] for the [Formula: see text] minimum, e.g., from [Formula: see text] to [Formula: see text], and a corresponding change in the [Formula: see text], e.g., from [Formula: see text] to [Formula: see text], with increasing tilt angle. Further, we exhibit a striking size dependence in the tilt angle interval for the vanishing of the [Formula: see text] and [Formula: see text] resistance minima, including "avoided crossing" type lineshape characteristics, and observable shifts of [Formula: see text] at the [Formula: see text] minima- the latter occurring for [Formula: see text] and the 10/7. The results demonstrate both size dependence and the possibility, not just of competition between different spin polarized states at the same [Formula: see text] and [Formula: see text], but also the tilt- or Zeeman-energy-dependent- crossover between distinct FQHE associated with different Hall resistances.