Low-temperature ultrafast mobility in systems with long-range repulsive interactions: Pb/Si(111).

A realization of the numerous phases predicted in systems with long-range repulsive interactions was recently found in Pb/Si(111). Surprisingly, these numerous phases can be grown at low temperatures approximately 40 K over macroscopic distances. This unusual observation can be explained from theoretical calculations of the collective diffusion coefficient D(c) in systems with long-range repulsive interactions. Instead of a gradual dependence of D(c) on coverage, it was found that D(c) has sharp maxima at low temperatures for every stable phase (i.e., for every rational value of the coverage theta=p/q) in agreement with the experiment.