Optically Induced Nuclear Spin Polarization in the Quantum Hall Regime: The Effect of Electron Spin Polarization through Exciton and Trion Excitations

摘要

We study nuclear spin polarization in the quantum Hall regime through theoptically pumped electron spin polarization in the lowest Landau level. Thenuclear spin polarization is measured as a nuclear magnetic field $B_N$ bymeans of the sensitive resistive detection. We find the dependence of $B_N$ onfilling factor unmonotonous. The comprehensive measurements of $B_N$ with thehelp of the circularly polarized photoluminescence measurements indicate theparticipation of the photo-excited complexes i.e., the exciton and trion(charged exciton), in nuclear spin polarization. On the basis of a novelestimation method of the equilibrium electron spin polarization, we analyze theexperimental data and conclude that the filling factor dependence of $B_N$ isunderstood by the effect of electron spin polarization through excitons andtrions.