Large skyrmions in an ${\mathrm{Al}}_{0.13}{\mathrm{Ga}}_{0.87}\mathrm{As}$ quantum well

We report tilted-field magnetotransport measurements of two-dimensional electron systems in a 200-Å-wide ${\mathrm{Al}}_{0.13}{\mathrm{Ga}}_{0.87}\mathrm{As}$ quantum well. We extract the energy gap for the quantum Hall state at Landau-level filling $\nu =1\mathrm{}$ as a function of the tilt angle. The relatively small effective Landé g factor $(g\simeq 0.043)$ of the structure leads to skyrmionic excitations composed of the largest number of spins yet reported $\left(s\simeq 50\right).$ Although consistent with the skyrmion size observed, Hartree-Fock calculations, even after corrections, significantly overestimate the energy gaps over the entire range of our data.