  The reentrant integer quantum Hall effects (RIQHE) are due to formation of
electronic crystals. We show analytically and numerically that topological
textures in the charge density distribution in these crystals in the vicinity
of charged defects strongly reduce energy required for current-carrying
excitations. The theory quantitatively explains sharp insulator-metal
transitions experimentally observed in RIQHE states. The insulator to metal
transition in RIQHE emerges as a thermodynamic unbinding transition of
topological charged defects.

Mesoscale and Nanoscale Physics