In the fractional quantum Hall effect regime we measure diagonal (ρxx) and Hall (ρxy) magnetoresistivity tensor components of two-dimensional electron system (2DES) in gated GaAs/AlxGa1−xAs heterojunctions, together with capacitance between 2DES and the gate. We observe 1/3- and 2/3-fractional quantum Hall effect at rather low magnetic fields where corresponding fractional minima in the thermodynamical density of states have already disappeared manifesting complete suppression of the quasiparticle energy gaps.
@article{arxiv.cond-mat/0603835,
title = {Fractional quantum Hall effect without energy gap},
author = {S. S. Murzin and S. I. Dorozhkin and G. E. Tsydynzhapov and V. N. Zverev},
journal= {arXiv preprint arXiv:cond-mat/0603835},
year = {2009}
}