Suppression of nuclear spin diffusion at a GaAs/AlxGa1-xAs interface measured with a single quantum-dot nanoprobe

Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlxGa1-xAs interface quantum dots by detecting the time dependence of the Overhauser shift in photoluminescence spectra. Long nuclear polarization decay times of approximate to 1 min have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin-diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.