Observation of inter-edge magnetoplasmon mode in a degenerate   two-dimensional electron gas
  We study the propagation of edge magnetoplasmons by time-resolved current measurements in a sample which allows for selective detection of edge states in the quantum Hall regime. We observe two decoupled modes of edge and inter-edge magnetoplasmons at filling factors close to 3. From the analysis of the propagation velocities of each mode the internal spatial parameters of the edge structure are derived. 
G. Sukhodub, F. Hohls and R. J. Haug