MICROWAVE RESONANCES IN LOW-FILLING INSULATING PHASE OF 2-DIMENSIONALELECTRON-SYSTEM

We present data on finite frequency (0.2 less than or equal to f less than or equal to 8.6 GHz) conductivity, Re(sigma(xx)), of the insulato r terminating in a fractional quantum Hall effect series in the high m agnetic field (B) limit. As B is increased within the insulator, at te mperatures of 50 and 200 mK Re(sigma(xx)) vs f evolves from a decreasi ng curve into a peak. The height and f of the peak increase with B. In tegrals of Re(sigma(xx)) vs f become B-independent at large enough B. The results are discussed within the framework of the Fukuyama-Lee mod el of the dynamics of a pinned Wigner crystal. (C) 1997 Published by E lsevier Science Ltd.