A Model for the Voltage Steps in the Breakdown of the Integer Quantum   Hall Effect
  In samples used to maintain the US resistance standard the breakdown of the dissipationless integer quantum Hall effect occurs as a series of dissipative voltage steps. A mechanism for this type of breakdown is proposed, based on the generation of magneto-excitons when the quantum Hall fluid flows past an ionised impurity above a critical velocity. The calculated generation rate gives a voltage step height in good agreement with measurements on both electron and hole gases. We also compare this model to a hydrodynamic description of breakdown. 
A. M. Martin, K.A. Benedict, F.W. Sheard and L. Eaves (University of   Nottingham)