Optically Pumped NMR Evidence for Finite-Size Skyrmions in GaAs Quantum Wells near Landau Level Filling ν  =  1

The Knight shift [K_s(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. K_s(ν) [proportional to the electron spin polarization 〈S_z(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→2 / 3.