Multicomponent fractional quantum Hall states with subband and spin degrees of freedom

In wide GaAs quantum wells where two electric subbands are occupied we apply a parallel magnetic field or increase the electron density to cause a crossing of the two N = 0 Landau levels of these subbands and with opposite spins. Near the crossing, the fractional quantum Hall states in the filling factor range 1 < ν < 3 exhibit a remarkable sequence of pseudospin polarization transitions resulting from the interplay between the spin and subband degrees of freedom. The field positions of the transitions yield a new and quantitative measure of the composite Fermions’ discrete energy level separations. Surprisingly, the separations are smaller when the electrons have higher spin-polarization. An interacting two-dimensional electron system (2DES) exhibits numerous fractional quantum Hall states (FQHSs) when it is subjected to a large perpendicular magnetic field (B⊥) and electrons occupy the lowest (N = 0) Landau levels (LLs) [1, 2]. These incompressible many-body states can be explained by composite Fermions (CFs), quasiparticles formed by attaching an even number (2p) of quantized flux quanta to each electron [2–4]. When B⊥ deviates from half-integer fillings, the CFs form their own discrete energy levels, the so