PINNING AND CONDUCTIVITY OF A 2-DIMENSIONAL CHARGE-DENSITY WAVE IN A STRONG MAGNETIC-FIELD

We investigate the dynamics of a two-dimensional electron system in a high magnetic field in the Wigner-crystalline regime where charge-density-wave correlations extend over a distance large compared with the interelectronic spacing. We determine the effects of weak disorder and of screening by uncondensed carriers of the internal electric fields produced by crystal deformation. We show, in agreement with previous work, that in the presence of disorder a dispersing, albeit inhomogeneously broadened mode exists even at wavelengths long compared with the positional correlation length. We obtain expressions for the line shape of the mode in terms of properties of the disorder. We compare our results to presently available data, concluding that present observations imply a correlation length of order one lattice constant at very large fields. However, threshold field measurements at smaller fields near the nu = 1/5 fractional quantum Hall plateau imply much larger correlation lengths, suggesting an anomalous field dependence of system properties.