Two-subband quantum Hall effect in parabolic quantum wells
  The low-temperature magnetoresistance of parabolic quantum wells displays pronounced minima between integer filling factors. Concomitantly the Hall effect exhibits overshoots and plateau-like features next to well-defined ordinary quantum Hall plateaus. These effects set in with the occupation of the second subband. We discuss our observations in the context of single-particle Landau fan charts of a two-subband system empirically extended by a density dependent subband separation and an enhanced spin-splitting g*. 
C. Ellenberger, B. Simovic, R. Leturcq, T. Ihn, S.E. Ulloa, K.   Ensslin, D. C. Driscoll and A. C. Gossard