2D WIGNER SOLID OVER LIQUID-HELIUM - RESONANT AND NONLINEAR PHENOMENA

Results are presented of an experimental study of coupled phonon-rippl on resonances in the Wigner crystal over a liquid helium surface in hi gh driving fields. The resonant frequencies are shown to be in a good agreement with existing theoretical results in the limit of lour excit ing signal. Novel additional resonances appear at lour frequencies for high driving fields, The mobility of the Wigner crystal at fixed freq uency, measured as a function of driving field, is essentially nonmono tonic showing a mobility jump in high enough driving fields.