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NONLINEAR OPTICAL PHENOMENA GENERATED BY SPATIALLY SEPARATED LIGHT BEAMS IN EXCITON SUPERFLUID STATE

激子超流体状态下空间分离的光束产生的非线性光学现象

基本信息

批准号：
10640310
负责人：
AIHARA Masaki
金额：
$ 1.98万
依托单位：
NARA INSTITUTE OF SCIENCE AND TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The nature of high-density electron-hole (e-h) systems induced by an intense optical field has received considerable attention because of the attractive possibility of the Bose-Einstein condensation (BEC) and superfluidity of excitons. Recent developments in the experimental techniques make it possible the simultaneous measurements of the spectroscopic and transport properties. In particular, the fast and coherent propagat ions of high-density excitons were observed in Cu_2O and BiI_3. These phenomena arise from the macroscopic quantum coherence of condensed exciton systems, because the fast exciton transport is more pronounced with increasing the exciton density. However, current understanding of these results still remain tentative and unclear because of the complicated situation, such as the polariton effect, the spatial inhomogeneity of exciton density, the finite life-time of excitons, the phonon effect and so forth. In this research project, we have *oretically investigated for the first time the anomalous transport phenomenon of two-dimensional excitons with large oscillator strength, taking into account the exciton-exciton interaction and the polariton effect. The equation-of-motion for expectation value of the exciton polariton operator with respect to the macroscopic quantum state has been derived by the decoupling approximation assuming that the macroscopic quantum coherence is maintained. The numerical solution shows the significant deviation from the simple ballistic (or diffusive) polariton propagation. This result indicates that the exciton-exciton interaction considerably enhances the fast coherent propagation of exciton polaritons in the high-density state. This analysis provides us with the proper interpretation of not iceable experiments on the transport phenomena in high-density exciton systems.

由于激子的玻色-爱因斯坦凝聚（BEC）和超流性，强光场诱导的高密度电子-空穴（e-h）系统的性质受到了广泛的关注。实验技术的最新发展使光谱和输运性质的同时测量成为可能。特别是在Cu_2O和BiI_3中观察到高密度激子的快速相干传播。这些现象源于凝聚态激子系统的宏观量子相干性，因为激子的快速输运随着激子密度的增加而更加明显。然而，由于激子的极化激元效应、激子密度的空间不均匀性、激子的有限寿命、声子效应等复杂的情况，目前对这些结果的理解仍然是初步的和不清楚的。在本研究计划中，我们首次从理论上研究了二维激子在大振子强度下的反常输运现象，考虑了激子-激子相互作用和极化激元效应。在保持宏观量子相干性的前提下，利用退耦近似导出了激子极化激元算符期望值相对于宏观量子态的运动方程.数值解显示了与简单的弹道（或扩散）极化激元传输的显着偏差。这一结果表明，激子-激子相互作用显著增强了高密度态激子极化激元的快速相干传输。这一分析为我们解释高密度激子系统中的输运现象提供了正确的解释。