We apply polarization resolved photoluminescence spectroscopy to measure the spin polarization of a two dimensional electron gas in perpendicular magnetic field. In the vicinity of filling factor nu=5/2, we observe a sharp discontinuity in the energy of the zero Landau level emission line. We find that the splitting between the two circular polarizations exhibits a sharp drop at nu=5/2 and is equal to the bare Zeeman energy, which resembles the behavior at even filling factors. We show that this behavior is consistent with filling factor nu=5/2 being unpolarized.
@article{arxiv.1005.3112,
title = {Optical Probing of the Spin Polarization of the nu=5/2 Quantum Hall State},
author = {M. Stern and P. Plochocka and V. Umansky and D. K. Maude and M. Potemski and I. Bar-Joseph},
journal= {arXiv preprint arXiv:1005.3112},
year = {2015}
}