Fractional quantum Hall effect in second subband of a 2DES

• Published in: Europhysics letters Vol. 94; no. 3; pp. 37010 - 37015
• Main Authors: Duarte, C. A, Armas, L. E. G, da Silva, E. C. F, Gusev, G. M, Bakarov, A. K, Wiedmann, S, Portal, J. C
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.05.2011; EPS, SIF, EDP Sciences and IOP Publishing
• Subjects: 71.30.+h; 73.40.Qv
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/94/37010

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.