Optically pumped NMR evidence for finite-size Skyrmions in GaAs quantum wells near Landau level filling ν=1

The Knight shift [Ks(ν,T)] and spin-lattice relaxation time [T1(ν,T)] of the 71Ga nuclei located in n-doped GaAs quantum wells are measured using optically pumped NMR, for Landau level filling 0.66<ν<1.76 and temperature 1.55<T<20 K. Ks(ν) [proportional to the electron spin polarization Sz(ν) drops precipitously on either side of ν=1, which is evidence that the charged excitations of the ν=1 ground state are finite-size Skyrmions. For ν<1, the data are consistent with a many-body ground state which is not fully spin polarized, with a very small spin excitation gap that increases as ν→23.