Dynamics of Optically Established Quantum Condensate Phases in Semiconductors

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（如碱-爱因斯坦凝聚（BEC））中激子质量相干运动的非线性光学响应。通过观察样品表面空间隔离的两个激光光斑在空间分辨区引起的共振发光和简并四波混频（DFWM）光。在BiI_3中，利用调至SFE态的皮秒激光在光斑激发下的空间分辨和时间分辨光致发光研究了被限制在准二维层错界面（SFE）中的激子的空间扩展。应用非线性薛定谔方程（Gross-Pitaevski方程），考虑弱排斥激子-激子相互作用，分析了发光强度的时空演化。结果表明，激子质量的膨胀与观测结果一致。DFWM光的发射是由于激子质量从一个点到另一个点的相干输运，这表明SFE质量明显处于凝聚态。另一方面，在GaSe中，激子在重激发下的发光表现为与其他激子或载流子散射而产生的反冲过程。在高密度的发光过程中，能量较大的激子之间的非弹性散射主导了激子质量的动力学过程，揭示了反冲发光，并在DFWM激发光谱上表现出显著的响应。结果表明，与BiI_3 SFE系统相反，激子之间的这种强排斥性相互作用阻止了它们的相干量子凝聚相的建立。在GaAs/AlAs系统的量子线结构中，研究了重激发激子的动力学行为及其弛豫过程。发现激子之间的排斥相互作用带来了显著的光谱蓝移和位置填充效应。这种奇特的行为被认为是低维激子系统的一个特征。在其他材料中，如Alq_3，光收集树突状大分子，π共轭导电聚合物：聚噻吩，高发光六核6-甲基吡啶乙醇铜(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，关于激子-激子相互作用和多体效应，明确了一些有趣的光学响应和弛豫过程。细节是未来的问题。少

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