Delocalized Wigner lattice on a dielectric layer with a metallic substrate: Dynamical properties and phase transitions

Properties of a two-dimensional Wigner lattice are analyzed taking into account delocalization of electrons on a thin dielectric layer with a metallic substrate. Electronic screening arising from the metallic substrate enhances the image potential as compared to the semi-infinite dielectric layer, but at the same time lowers the electron-electron interaction. As a result, the electron delocalization becomes a complicated function of the dielectric thickness, dielectric constant, and the electron density. The electron ground-state energy is calculated including the k=0 term of the lattice potential, which has a significant effect at high electron densities. The influence of electron delocalization and of the dielectric substrate on the electron lattice dynamics (phonon spectra, sound velocities) and on the Wigner phase transition is demonstrated. In particular, possible extension of the Kosterlitz-Thouless melting criterion to the quantum regime is discussed.