Coupling of the triplet states of a negatively charged exciton in a quantum dot with the spin of a magnetic atom
Résumé
Two electrons in a quantum dot (QD) can form triplet states. We analyze the exchange coupling of the triplet states of the negatively charged exciton in a QD (X- , two electrons and one hole) with the spin of a magnetic atom (Mn). Two techniques are used to access the spin structure of this magnetic complex: the resonant excitation of the excited states of X--Mn and the analysis of the emission of a negatively charged biexciton in a magnetic dot (XX −-Mn). The photo-luminescence (PL) excitation of X −-Mn reveals excited states with a circularly polarized fine structure which strongly depends on the Mn spin state Sz and gives rise to negative circular polarization emission. This fine structure arises from the coupling of the triplet states of an excited charged exciton with the Mn (X − *-Mn) and its Sz dependence can be described by a spin effective model. The recombination of XX −-Mn leaves in the dot a charged exciton in its excited state and the PL structure is controlled by the coupling of triplet states of X − * with the Mn spin. An analysis of the polarization and magnetooptic properties of this emission gives access to the electron-hole exchange interaction within the triplets states. Comparing the fine structure of the singlet X −-Mn and of the triplets of X − *-Mn we can independently study the different source of anisotropy in the QD: the valence band mixing and the exchange interaction in an anisotropic potential.
Domaines
Matière Condensée [cond-mat]Origine | Fichiers produits par l'(les) auteur(s) |
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