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Séminaire: Kimberley Hall

Date : 16 janvier 2019

Type : Séminaires

Lieu : D3-2041

Kimberley Hall Department of Physics and Atmospheric Science, Dalhousie University Titre: Ultrafast Quantum Control of Charge and Spin in Semiconductors Résumé: During this seminar, I will highlight some of the recent research projects carried out in the Ultrafast Quantum Control Group at Dalhousie University. Our group has developed pulse shaping techniques for optimizing quantum state manipulation in individual semiconductor quantum dots for application to solid state emitters and quantum information platforms. We have also applied ultrafast spectroscopy techniques to the study of charge and spin dynamics in hybrid organic-inorganic perovskite materials, including four-wave mixing to study the impact of many-body effects and time-resolved circular dichroism to probe carrier spin relaxation. For this seminar, I will primarily focus on the latter work. The hybrid perovskites are semiconductors that contain both organic and inorganic constituents (e.g. the most well-studied material in this class is CH3NH3PbI3) . While these materials have gained considerable attention in recent years due to their applicability to high-efficiency solar cells, they also hold great promise for applications in semiconductor spintronics and quantum information science, in which information is encoded in the spin state of the charge carriers. This potential is due to the large spin-orbit interaction, which provides a means to manipulate the spin state using an applied bias through the Rashba effect. Numerous theoretical studies have predicted ultralarge Rashba effects in the hybrid perovskites due to the incorporation of heavy elements (e.g. Pb, Sn, I) and the breaking of inversion asymmetry via distortions of the metal-halide octahedra. The flexibility in the choice of organic cations, which control the magnitude and symmetry of the octahedral distortions, enables the Rashba effect to be tailored in these materials for a particular device application. Despite this promise, experimental studies of the spin-related properties of these materials remain scarce. Our group has recently carried out polarization-dependent pump probe studies of the 2D perovskite butylammonium methylammonium lead iodide and related 2D systems [1]. Our results experimentally verify the presence of Rashba coupling in this system and demonstrate the utility of spin relaxation as a probe of such effects. These findings highlight the strong potential of the hybrid perovskite semiconductors for the development of spin-related technologies. [1] S. B. Todd et al., cond-mat arXiv:1807.10803 (2018).

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