Negative Differential Resistance and Astability of the Wigner Solid
  We report an unusual breakdown of the magnetically induced Wigner solid in an exceptional two-dimensional electron gas. The current-voltage characteristic is found to be hysteretic in the voltage biased setup and has a region of negative differential resistance in the current biased setup. When the sample is current biased in the region of negative differential resistance, the voltage on and the current through the sample develop spontaneous narrow band oscillations. 
G.A. Csathy, D.C. Tsui, L.N. Pfeiffer, and K.W. West