ANOMALOUS BEHAVIOR ABOVE THE MELTING-POINT OF 2-DIMENSIONAL ELECTRONSON LIQUID-HELIUM

Anomalous fluctuations in magnetoconductance are observed above the me lting temperature T-m of two-dimensional electrons on liquid He-4. In the 2D solid the low frequency Corbino magnetoconductivity sigma(B) is increased by coherent Bragg-Cerenkov coupling to ripplons on the heli um surface. Above T-m (plasma parameter Gamma = 127), fluctuations in sigma(B) suggest a microstructure with significant ordered and coupled regions. The fluctuations decrease continuously with temperature up t o T-f = (2.8 +/- 0.3)T-m at Gamma = 46 +/- 5. Fluctuations also occur in the 2D electron solid at high drive amplitudes.