Universal features of single particle and collective localization along the ν=1 integer quantum Hall plateau*

Integer quantum Hall plateaus in low disorder two-dimensional electron gases exhibit both single particle and collective localization. The former is associated with an Anderson insulator, while the latter with a Wigner solid called the integer quantum Hall Wigner solid. We find that in two samples of different densities the layout of the phase stability diagram is similar, highlighting therefore density-independent universal properties of the two insulating phases. Furthermore, the two insulating phases develop at different magnetic fields and different quasiparticle densities, but at similar ranges of filling factors. These properties are inconsistent with a classical electron solid and underline therefore the quantum nature of the integer quantum Hall Wigner solid. The transition or crossover from the Anderson insulator to the integer quantum Hall Wigner solid remains poorly understood.