Effects of the electron density on the phase stability diagram of the ν=1 integer quantum Hall state in ultra-high quality two-dimensional electron gases

The crossover from the Anderson insulator to the integer quantum Hall Wigner solid in the integer quantum Hall regime remains poorly understood. The former develops in the middle of the ν=1 plateau, whereas the latter in the flanks of the ν=1 plateau. We find that these two phases are universally present in ultra-high quality GaAs samples grown using the latest generation state-of-the-art MBE techniques. We will discuss effects of the sample density on the phase stability diagram as measured in the 0.42 -1 x 10^11/cm² range. To our surprise, we find that the filling factor of the phase boundary between the integer quantum Hall Wigner solid and the Anderson insulator changes very little with electron density. Other properties of these two phases, including implications of skyrmion physics, will also be discussed.