Resonant spin orientation at the exciton level anticrossing in InP quantum dots

Abstract

Resonant spin orientation of excitons was observed under linearly polarized quasiresonant excitation around two anticrossing points of excitons in InP quantum dots (QDs). Under the longitudinal and tilted magnetic fields of 1.5 and $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{T}$, two anticrossings of bright and dark excitons take place. At the anticrossing points, bright and dark excitons mix with each other and the wave function mixing induces the resonant spin orientation. Time-resolved circular polarization clearly showed the resonant spin orientation due to mixing of bright and dark excitons at the anticrossing points. Dark excitons can work as the carrier and spin reservoir because of their long lifetime. We demonstrated that magnetic field can control the spin entanglement and the resonant spin orientation of QDs.