High magnetic-field microwave conductivity of two-dimensional electrons in an array of antidots

We find the high magnetic field ~B! microwave conductivity @Re(sxx)# of a two-dimensional electron system containing an antidot array increases strongly with frequency ~f! in the regime with Landau filling 1/3,n,2/3. At microwave f , Re(sxx) vs B exhibits a broad peak centered around n51/2. On the peak, Re(sxx) at 10 GHz can be five times its dc-limit value. Unlike the dc-limit conductivity, the microwave conductivity is extremely temperature ~T! sensitive, increasing as T decreases down to 100 mK ~the lowest T measured! and disappearing above 0.5 K. The enhanced microwave conductivity is apparently due to antidot edge excitations of fractional quantum Hall effect states, and may be associated with the chiral Luttinger liquids.