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Dynamics of Optically Established Quantum Condensate Phases in Semiconductors

半导体中光学建立的量子凝聚相的动力学

基本信息

批准号：
14340095
负责人：
KARASAWA Tsutomu
金额：
$ 7.62万
依托单位：
Osaka City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340095/
关键词：
layered semiconductors BiI_3 stacking fault exciton GaSe coherent propagation of excitons Bose-Einstein Condensation of excitons degenerate four-wave-mixing nonlinear optical responses Gross-Pitaevski equation 励起子のボーズ凝縮非線形光学応答

项目摘要

In layered crystals BiI_3, and GaSe, we have studied spatial and temporal behavior of high-density exciton masses and their nonlinear optical response in connection with coherent motion of the exciton masses in a photo-induced quantum condensed phase such as the Base-Einstein condensation (BEC), by observing spatial expansion of the resonance luminescence and the degenerate four-wave-mixing (DFWM) light induced by spatially isolated two laser-light spots on the sample surface in the space-resolved regime.In BiI_3, spatial expansion of the excitons confined in a quasi tow-dimensional stacking fault interface (SFE) was examined in the space- and time-resolved photoluminescence under the spot excitation with a picosecond laser light tuned to the SFE state. The space and time evolution of the luminescence intensity was analyzed by applying a nonlinear Schrodinger equation (Gross-Pitaevski equation) by considering weakly repulsive exciton-exciton interaction. It shows that the expansion of … More the exciton masses is reproduced in accordance with the observed results. The DFWM light was emitted owing to the coherent transport of the exciton masses from one to the other spot sites showing evidently the SFE masses being in a condensed phase. On the other hand, in GaSe, the exciton luminescence under heavy excitation is characterized by the recoil process due to scattering with the other excitons or carriers. In the luminescence process at high density, the inelastic scattering between excitons with relatively large energies governs dominantly the dynamical process of exciton masses revealing the recoil luminescence, and showing also the remarkable response on the DFWM excitation spectra. It turns out that this strongly repulsive interaction between excitons prevents the establishment of their coherent quantum condensed phase, in contrast to the case of the BiI_3 SFE system.In the quantum wire structures of GaAs/AlAs system, dynamical behavior of the heavily excited excitons and their relaxation process have been examined. It is found that a repulsive interaction between excitons brings about remarkable spectral blue-shifts and site-filling effects. The curious behavior is understood to be a characteristic in low dimensional exciton systems.In other materials, such as Alq_3, light-harvesting dendrimers, π-conjugated conducting polymer : polythiophene, highly luminescent hexanucler 6-methylpyridinetholato copper(1), we have investigated exciton transitions and luminescence spectra under high density excitation. In these materials some interesting optical responses and relaxation processes are made clear with respect to the exciton-exciton interaction and many-body effects. The details are future problems. Less

在层状晶体BiI_3和GaSe中，我们研究了高密度激子质量的时空行为及其与光致量子凝聚相（如Base-Einstein凝聚（BEC））中激子质量相干运动有关的非线性光学响应。通过观察空间隔离的两束激光诱导的共振发光和简并四波混频光的空间扩展，在BiI_3晶体中，用皮秒激光调制到准二维堆垛层错界面（SFE）态，在点激发下，用空间分辨和时间分辨的光致发光方法研究了半导体材料中准二维SFE界面中激子的空间扩展.考虑激子-激子间的弱排斥作用，应用非线性薛定谔方程（Gross-Pitaevski方程）分析了发光强度的时空演化.它表明， ...更多信息激子质量根据观察结果再现。由于激子质量从一个点到另一个点的相干输运而发射DFWM光，这表明SFE质量处于凝聚相。另一方面，在GaSe中，重激发下的激子发光的特征在于由于与其他激子或载流子散射而产生的反冲过程。在高密度发光过程中，能量较大的激子之间的非弹性散射主导着激子质量的动力学过程，表现出反冲发光，并对DFWM激发谱有显著的响应。在GaAs/AlAs系统的量子线结构中，研究了重激发态激子的动力学行为及其弛豫过程。发现激子间的排斥作用引起了光谱蓝移和晶格填充效应。在其他材料中，如Alq_3、捕光树枝状大分子、π共轭导电聚合物：聚噻吩、高发光六核6-甲基吡啶硫醇合铜（1），我们研究了高密度激发下的激子跃迁和发光光谱。在这些材料中，一些有趣的光学响应和弛豫过程是明确的激子-激子相互作用和多体效应。细节是未来的问题。少