Fluctuations and Shear Modulus of a Classical Two-Dimensional Electron Solid: Experiment

The shear modulus of two-dimensional electrons at the surface of liquid helium is deduced from measurements of the finite frequency of the $k\to 0$ limit of the coupled electron-substrate transverse sound mode. Its behavior on the approach to melting is compatible with the Kosterlitz-Thouless model for two-dimensional melting.