Evolution of the bilayer nu = 1 quantum Hall state under charge   imbalance
  We use high-mobility bilayer hole systems with negligible tunneling to examine how the bilayer nu = 1 quantum Hall state evolves as charge is transferred from one layer to the other at constant total density. We map bilayer nu = 1 state stability versus imbalance for five total densities spanning the range from strongly interlayer coherent to incoherent. We observe competition between single-layer correlations and interlayer coherence. Most significantly, we find that bilayer systems that are incoherent at balance can develop spontaneous interlayer coherence with imbalance, in agreement with recent theoretical predictions. 
W.R. Clarke, A.P. Micolich, A.R. Hamilton, M.Y. Simmons, C.B. Hanna,   J.R. Rodriguez, M. Pepper and D.A. Ritchie