Quantum Hall effect in a wide parabolic quantum well

We investigate the activated conductivity for Landau levels at filling fact ors v=1,2 in a parabolic AlxGa1-xAs well down to 30 mK. We obtain a very sm all activation energy similar to 0.02 meV, which is almost 1-2 orders of ma gnitude smaller than the expected values for energy gaps in a wide quantum well. The resistivity minima vanish completely when a parallel component of magnetic field is applied. The collapse of the energy gaps in the wide par abolic well occurs due to the new electron correlated state, probably the c harge density wave state predicted for a uniform wide electron slab in high magnetic field.