Observation of narrow-band noise accompanying the breakdown of   insulating states in high Landau levels
  Recent magnetotransport experiments on high mobility two-dimensional electron systems have revealed many-body electron states unique to high Landau levels. Among these are re-entrant integer quantum Hall states which undergo sharp transitions to conduction above some threshold field. Here we report that these transitions are often accompanied by narrow- and broad-band noise with frequencies which are strongly dependent on the magnitude of the applied dc current. 
K.B. Cooper, J.P. Eisenstein, L.N. Pfeiffer, K.W. West