| Research Abstract |
(1) Many body effects and dynamics of excitons in AlGaAs/AIAs semiconductor quantum wires
Many body effects and their dynamics of excitonic photoluminescence (PL) in Al_xGa_<1-x>As/AlAs semiconductor quantum wires (QWR's) have been studied. It has been clarified that an accumulation dynamics of the excitons among the QWR's plays an important role on the dynamics of the many body effects. And as a result, a phase space filling effect of the high density excitons gives rise to the blue shift of the PL under high density excitation. On the other hand, an asymmetric diffusion of the excitons along the QWR's was observed. Under high density excitation, an enhancement of the exciton diffusion has been revealed.
(2) Many body effects and dynamics of excitons in nano-interfaces of layered semiconductors
Temporal and spatial dynamics of the excitons localized at the nano-interface in BiI_3, have been investigated by a spatially resolved degenerated four wave mixing technique. As a result, It has b
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een clarified that the quantum state of the excitons propagate macroscopically in keeping the quantum coherency. The spatial propagation dynamics of the exciton quantum states can be explained by a Gross-Pitaevskii equation including a weak repulsive interaction among excitons.
(3) Many body effects and dynamics of excitons in semiconductor microcrystallites in matrices
Microcrystallites of Cul, HgI_2,PbI_2 and TII embedded in the porus polymers and glasses have been grown. Many body effects and exciton-lattice interactions of the excitons in the microcrystallites have been studied. In Cul and HgI_2, novel crystal structures and novel exciton transitions appear as a result of micro-crystallization. On these exciton system, nonlinear luminescences of the bi-excitons and the inelastic scattering of the excitons were observed. It has been cleared that the mechanism of the many body effects changes by changing the crystal size, temperature and excitation density. On the other hand, on the microcrystallites of TII, HgI_2 and PbI_2, the exciton-lattice interactions are enhanced by the interaction between the microcrystallites and matrices. In the case of TII and HgI_2, the effective energy transfer from the matrices to the maicrocrystallites governs the dynamics of the nonlinear luminescence of the excitons.
(4) Dynamics of excitons in functional organic semiconductor nano-molecules
Dynamics of the photo-excited states providing the luminescence of the luminous organic dye Alq3 and the hexanuclear 6-Methylpyridinethiolato-Copper (I) have been studied. On the Alq3, we have proposed a new model for the photo-excited state including two-luminescent states and a intermediate state mediating thermal activation. On the other hand, the origin and dynamics of the photo excited states have been revealed. Less
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