Correlated states of electrons in wide quantum wells at low fillings: The role of charge distribution symmetry

Magnetotransport measurements on electrons confined to a 57-nm-wide, GaAs quantum well reveal that the correlated electron states at low Landau level fillings (ν) display a remarkable dependence on the symmetry of the electron charge distribution. At a density of 1.93×1011cm-2, a developing fractional quantum Hall state is observed at the even-denominator filling ν=1/4 when the distribution is symmetric, but it quickly vanishes when the distribution is made asymmetric. At lower densities, as we make the charge distribution asymmetric, we observe a rapid strengthening of the insulating phases that surround the ν=1/5 fractional quantum Hall state.