Magnetic-field-induced insulating phases at large rs

Exploring a two-dimensional hole system in the large rs regime we found a surprisingly rich phase diagram. At the highest densities, beside the ν=1/3, 2/3, and 2/5 fractional quantum Hall states, we observe both of the previously reported high field insulating and reentrant insulating phases. As the density is lowered, the reentrant insulating phase initially strengthens, then it unexpectedly starts weakening until it completely disappears. The intricate behavior of the insulating phases can be explained by a nonmonotonic melting line in the ν-rs phase space.