Evidence for a Liquid-to-Crystal Phase Transition in a Classical, Two-Dimensional Sheet of Electrons

Abstract

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\ifmmode\times\else\texttimes\fi{}${10}^{8}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ to 9\ifmmode\times\else\texttimes\fi{}${10}^{8}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ and has yielded melting temperatures between 0.35 and 0.65 K. The phase transition occurs at $\ensuremath{\Gamma}=137\ifmmode\pm\else\textpm\fi{}15$, where $\ensuremath{\Gamma}$ is a measure of the ratio of potential energy to kinetic energy per electron.