Reentrant nu = 1 quantum Hall state in a two-dimensional hole system
  We report the observation of a reentrant quantum Hall state at the Landau level filling factor nu = 1 in a two-dimensional hole system confined to a 35-nm-wide (001) GaAs quantum well. The reentrant behavior is characterized by a weakening and eventual collapse of the nu = 1 quantum Hall state in the presence of a parallel magnetic field component B||, followed by a strengthening and reemergence as B|| is further increased. The robustness of the nu = 1 quantum Hall state during the transition depends strongly on the charge distribution symmetry of the quantum well, while the magnitude of B|| needed to invoke the transition increases with the total density of the system. 
A.L. Graninger, D. Kamburov, M. Shayegan, L.N. Pfeiffer, K.W. West,   K.W. Baldwin, and R. Winkler
cond-mat.mes-hall