Microwave spectroscopic observation of a Wigner solid within the ν=1/2 fractional quantum Hall effect

We have studied the microwave spectra of a wide quantum well for Landau level fillings, ν, just below 1/2, under conditions where the ν=1/2 fractional quantum Hall effect (FQHE) is present. One resonance in the spectra exhibits intensity variations with ν in striking agreement with that expected for a pinning mode of a Wigner solid of quasiholes of this FQHE state. This resonance is also quite sensitive to asymmetrization of the growth-direction charge distribution in the quantum well by gate bias. Another resonance in the spectra is associated with a different bilayer Wigner solid that also exists at much lower ν than the 1/2 FQHE, and that appears to coexist with the 1/2 quasihole solid.