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 (ν) between 1/5 and 2/9. The magnetoconductivity in the RIP has resonant behavior around 150 MHz, showing a peak at ν~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<ν<1/2 and we have revealed features, not seen in DC transport, that suggest some intriguing interplay between the 1/3 FQHE and RIP.