Photoluminescence fine structures and neutral collective excitations of fractional quantum Hall fluids in wide GaAs quantum wells

Interactions between two-dimensional electron gas and photoexcited holes localized under high magnetic fields offer a sensitive probe of fractional quantum hall fluids. We uncover the crossover of photoluminescence (PL) from Landau level transitions and many body excitons to trions with increasing magnetic field. Surprisingly, in wide GaAs quantum wells the magnetic field induces an unexpected large number of splittings of all PL features. Circular polarized PL resolves the important role of valence band mixing and may suggest a broken rotational symmetry in the lowest Landau level. On the other hand, neutral collective excitations probed by resonant inelastic light scattering are found to possess multiple resonances corresponding to the PL complex, which would provide critical scattering channels for the detection of chiral long-wavelength magnetoroton excitations predicted by geometrical description of the fractional quantum hall effect.