No abstract

The relative static stability of square and triangular dectron lattices (two-dimensional %'igner crystals), the instability against vibrational excitations, and the effect of image-potential-induced screening on the dispersion of the frequency spectra are studied in the inversion layer of a metal-insulator-semiconductor structure. In harmonic approximation the two-dimensional Wigner crystal turns out to be stable against transverse vibrations for a triangular lattice but unstable for a square lattice in the I10] direction in disagreement with previous calculations. In triangular lattices, the transition of the anomalous dispersion (coL~k '") of the two-dimensional longitudinal mode at intermediate wave vectors (D ' & k & a ') to the normal dispersion (el~k) in the extremely-long-wavelength limit (kD & 1) due to screening effects is studied as a function of the ratio of insulator thickness D and lattice constant a.

No abstract

No abstract