Anomalous temperature dependence of the correlated ν=1 quantum Hall effect in bilayer electron systems

In bilayer electron systems realized in wide single quantum wells with intermediate density, we observe a many-body quantum Hall state at Landau-level filling ν=1 stabilized by interlayer Coulomb interaction. This quantum Hall ground state makes a phase transition to a compressible state as density is increased. The unusual temperature and density dependence of the data as the transition boundary is approached is suggestive of an additional finite-temperature transition from a quantum Hall state to a compressible state, which is unique to bilayer systems.