EXCITATION SPECTRUM OF A 2-DIMENSIONAL WIGNER LATTICE

We propose a spectroscopic method to determine the existence of an ele ctronic Wigner lattice at a given electron density n. We derive the '' perpendicular'' excited states of the two-dimensional Wigner lattice o n a dielectric layer with a metallic substrate, and compare them with the corresponding excited states of the two-dimensional electron gas a t the same electron densities. The transitions from the ground to the first excited state are studied in detail and we have found a signific ant difference between the lattice and the gas excitation energies for n greater than or similar to 10(8) cm-2. In that sense, the spectrosc opy of electronic transitions can prove the existence of a Wigner latt ice and a rapid change in the excitation spectrum can serve for determ ination of the lattice melting temperature. A linear Stark effect in t he case of a Wigner lattice is also analyzed.