Observation of reentrant quantum Hall states in the lowest Landau level
  Measurements in very low disorder two-dimensional electrons confined to relatively wide GaAs quantum well samples with tunable density reveal reentrant $\nu=1$ integer quantum Hall states in the lowest Landau level near filling factors $\nu=4/5$ and 6/5. These states are not seen at low densities and become more prominent with increasing density and in wider wells. Our data suggest a close competition between different types of Wigner crystal states near these fillings. We also observe an intriguing disappearance and reemergence of the $\nu=4/5$ fractional quantum Hall effect with increasing density. 
Yang Liu, C. G. Pappas, M. Shayegan, L. N. Pfeiffer, K. W. West, and   K. W. Baldwin
cond-mat.mes-hall