Experimental evidence is presented for an electron-liquid to electron-crystal phase transition in a sheet of electrons on a liquid-He surface. The phase transition has been studied for electron areal densities from 3×${10}^8$ ${\mathrm{cm}}^{-2\mathrm{}}$ to 9×${10}^8$ ${\mathrm{cm}}^{-2\mathrm{}}$ and has yielded melting temperatures between 0.35 and 0.65 K. The phase transition occurs at $\Gamma =137\mathrm{}\pm 15$, where $\Gamma$ is a measure of the ratio of potential energy to kinetic energy per electron.

• Received 17 January 1979

DOI:https://doi.org/10.1103/PhysRevLett.42.795