Imaging of low-compressibility strips in the quantum Hall liquid

Using subsurface charge accumulation scanning microscopy, we image strips of low compressibility corresponding to several integer quantum Hall filling factors. We study in detail the strips at Landau level filling factors $\nu =2\mathrm{}$ and 4. The observed strips appear significantly wider than predicted by theory. We present a model accounting for the discrepancy by considering a disorder-induced nonzero density of states in the cyclotron gap.