Propriétés magnéto-optiques de nanocristaux de CdSe individuels à basse température

Abstract : The development of emerging applications of CdSe nanocrystals requires a detailed understanding of the band-edge exciton fine structure and relaxation pathways. This thesis is focused on cryogenic spectroscopy of single nanocrystal with a remarkable photostability. Photoluminescence spectra as a function of temperature and under external magnetic fields provide a spectral fingerprint of the low energy sub-levels, revealing the morphology and the crystal structure of individual nanocrystals. In order to probe the entire band-edge exciton fine structure, a high resolution luminescence excitation technique has been developed. Zeeman and anisotropy-induced splittings are used to reveal the entire 8-state band-edge fine structure, enabling complete comparison with band-edge exciton models. State selective excitation allows the preparation of single quantum states. It is also used to map the hole spin relaxation pathways between the fine structure sub-levels.Charged quantum dots provide an important platform for a range of emerging quantum technologies. Double shell CdSe nanocrystals are engineered to efficiently ionize at cryogenic temperatures, resulting in trion emission with a single sharp zero-phonon line and a near-unity quantum yield. Zeeman splitting of this line enables direct determination of electron and hole g-factors. Spin relaxation is observed in high fields, enabling identification of the trion charge. Importantly, we show that spin flips are completely inhibited for Zeeman splittings below the low-energy bound for confined acoustic phonons. This charac- teristic unique to colloidal quantum dots has potential applications in single spin coherent manipulation.
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Chiara Sinito. Propriétés magnéto-optiques de nanocristaux de CdSe individuels à basse température. Optique [physics.optics]. Université de Bordeaux, 2014. Français. ⟨NNT : 2014BORD0282⟩. ⟨tel-01194873⟩

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