NMR study of large skyrmions in Al_0.13Ga_0.87As quantum wells

A nuclear magnetic resonance (NMR) study is reported of multiple (30) Al_0.13Ga_0.87As quantum well (QW) sample near the Landau level filling factor ν=1. In these Al_0.13Ga_0.87As QWs the effective g factor is nearly zero. This can lead to two effects: vanishing electronic polarization (P) and skyrmionic excitations composed of a huge number of spins. As small P values cause an overlap of the NMR signals from the QW and barriers, a special technique was employed to allow these two signals to be distinguished. The QW signal corresponds to a small, negative, and very broad distribution of spin polarization that exhibits thermally induced depolarization. Such a distribution can be attributed to sample inhomogeneities and/or to large skyrmions, the latter possibility being favored by observation of a very fast T₂⁻¹ rate.