Nuclear and excitonic spin polarization formed using cross-linearly polarized pulse pair via half-localized state in a single self-assembled quantum dot

The oscillations of excitonic and nuclear spin polarizations in an optically pumped single self-assembled In0.8Al0.2As/Al0.35Ga0.65As quantum dot QD were clearly observed under the excitation of a wetting layer edge at B=5 T. This indicates that an exciton pair with opposite spins is alternatively created via the half-localized state only by changing the delay time between cross-linearly polarized pulse pair. Furthermore, periodic modulation of Zeeman energy synchronizes the degree of circular polarization of photoluminescence from a single QD, indicating that the Overhauser field follows the optically created electron spin polarization in half-localized states of a QD, and the half-localized state in a QD consists of a confined electron in a discrete state and hole in the continuum state