In a GaAs/AlGaAs quantum well of electron density 1x10^{11} cm^{-2} we observe a fractional quantum Hall effect (FQHE) at filling factors nu=4/11, and 5/13, and weaker states at nu=6/17, 4/13, 5/17 and 7/11. These sequences of fractions do not fit into the standard series of integral quantum Hall effects (IQHE) of composite fermions (CF) at nu=p/(2mp +/- 1). They rather can be regarded as the FQHE of CFs attesting to residual interactions between these composite particles. In tilted magnetic fields the nu=4/11 state remains unchanged, strongly suggesting it to be spin-polarized. The weak nu=7/11 state vanishes quickly with tilt.
@article{arxiv.cond-mat/0303429,
title = {Fractional Quantum Hall Effect of Composite Fermions},
author = {W. Pan and H. L. Stormer and D. C. Tsui and L. N. Pfeiffer and K. W. Baldwin and K. W. West},
journal= {arXiv preprint arXiv:cond-mat/0303429},
year = {2009}
}