AC Magnetotransport in Reentrant Insulating Phases of Two-dimensional   Electrons near 1/5 and 1/3 Landau fillings
  We have measured high frequency magnetotransport of a high quality two-dimensional electron system (2DES) near the reentrant insulating phase (RIP) at Landau fillings ($\nu$) between 1/5 and 2/9. The magneto\textit{conductivity} in the RIP has resonant behavior around 150 MHz, showing a \textit{peak} at $\nu$$\sim$0.21. Our data support the interpretation of the RIP as due to some pinned electron solid. We have also investigated a narrowly confined 2DES recently found to have a RIP at 1/3$<$$\nu$$<$1/2 and we have revealed features, not seen in DC transport, that suggest some intriguing interplay between the 1/3 FQHE and RIP. 
Yong P. Chen, Z. H. Wang, R. M. Lewis, P. D. Ye, L. W. Engel, D. C.   Tsui, L. N. Pfeiffer and K. W. West