Abstract
In the present paper we report on the experimental electron sheet density vs. magnetic field diagram for the magnetoresistance Rxx of a two-dimensional electron system (2DES) with two occupied subbands. For magnetic fields above 9 T, we found fractional quantum Hall levels centered around the filing factor ν=3/2 in both the two occupied electric subbands. We focused specially on the fractional levels of the second subband, whose experimental values of the magnetic field B of their minima do not obey a periodicity law in 1/|B−Bc|, where Bc is the critical field at the filling factor ν=3/2, and we explain this fact entirely in the framework of the composite fermions theory. We use a simple theoretical model to give a possible explanation for the fact.
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