Persistence of Vibrational Modes in a Classical Two-Dimensional Electron   Liquid
  Vibrational density of states of a classical two-dimensional electron system obtained with a molecular-dynamics simulation is shown to have a peak in both solid and liquid phases. From an exact diagonalisation of the dynamical matrix, the peak is identified to be vibrational modes having wavelengths of the order of the electron spacing, and the result is interpreted as persistent vibrational modes with short wavelengths in a liquid. 
Satoru Muto and Hideo Aoki