EDGE MELTING AND COLLECTIVE EDGE EXCITATIONS OF THE 2-DIMENSIONAL WIGNER CRYSTAL IN A STRONG MAGNETIC-FIELD

The edge electronic structure and collective excitations of a two-dimensional Wigner crystal are studied as a function of the strength of an external static potential that compresses the electrons at the edge of the crystal. It is demonstrated that, as the strength of the external confining potential is increased, the electrons at the edge may melt, giving rise to a phase of the two-dimensional electron gas in which the bulk is essentially crystalline, while the edge is melted. In the generalized random-phase approximation, this melting transition is signaled by the appearance of a collective mode which is gapless even in the presence of pinning centers, and is localized to the edge of the system. The consequences of this melting transition on the transport properties of the system are discussed.