  We study the optically pumped nuclear spin polarization in a single
GaAs/AlGaAs quantum well in the quantum Hall system. We apply resistive
detection via the contact hyperfine interaction, which provides high
sensitivity and selectivity, to probe a small amount of polarized nuclear spins
in a single well. The properties of the optical nuclear spin polarization are
clearly observed. We theoretically discuss the nuclear spin dynamics
accompanied with doped electrons to analyze the experimental data. The optical
nuclear polarization spectra exhibit electron-spin-resolved lowest Landau level
interband transitions. We find that the phonon emission process, which normally
assists the optical pumping process, influences the optical nuclear spin
polarization. We also discuss that the electron-electron interaction can play
an important role in the optical nuclear spin polarization.
