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Coherent Motion of Excited Electronic States in Layered Crystals

层状晶体中激发电子态的相干运动

基本信息

批准号：
11640321
负责人：
KARASAWA Tsutomu
金额：
$ 2.24万
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 (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

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 condensed phase such as the Bose-Einstein condensation (BEC).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 telegrapher's equation including damping. It shows that the degree of coherence increases with increasing exciton density. In order to obtain phase information of the high-density exciton masses, the degenerate four-wave-mixing (DFWM) light induced by spatially isolated two laser-light spots on the sample surface was detected in the space-resolved regime. The DFWM light … More was emitted owing to the coherent transport of the exciton mass from one to the other spot sites suggesting evidently the SFE-polariton masses being in the BEC phase. In GaSe, the exciton luminescence under heavy excitation is characterized by the recoil process due to scattering with the other excitons or carriers. The details of the dynamical scattering processes of the excitons have been made clear from space and time evolution, and spectral change of the recoil luminescence.In the theoretical work, the order formation and superfluidity have been investigated in a quasi-two dimensional Bose gas of excitons. We have calculated the elementary excitations, when the ground state is in the ordered state of the vortex-lattice, and examined the temperature dependence of the off-diagonal long range order which is the essential quantity specifying the condense state of the two-dimensional exciton system. We also calculate the melting temperature of the vortex-lattice assuming the Kosterlitz-Thouless type defect-mediated melting mechanism 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凝聚相（如玻色-爱因斯坦凝聚（BEC））中激子质量相干运动有关的非线性光学响应。研究了准二维堆垛层错界面中激子的空间扩展，在用调谐到SFE状态的皮秒激光的点激发下解析的光致发光。应用含阻尼的电报方程分析了发光强度的时空演化。结果表明，相干度随激子密度的增加而增加。为了获得高密度激子质量的相位信息，在空间分辨的制度下，在样品表面上的空间隔离的两个激光光斑诱导的简并四波混频（DFWM）光被检测到。DFWM灯 ...更多信息的发射由于相干传输的激子质量从一个到其他点的网站表明显然超临界流体极化激元质量在BEC阶段。在GaSe中，在重激发下的激子发光的特征在于由于与其它激子或载流子的散射而引起的反冲过程。从激子的时空演化和反冲发光的光谱变化，阐明了激子的动力学散射过程的细节，在理论工作中，研究了准二维玻色激子气体中的有序形成和超流性。我们计算了基态处于涡格有序态时的元激发，并研究了描述二维激子系统凝聚态的基本量--非对角长程有序度与温度的关系。我们还计算了假设Kosterlitz-无缺陷型缺陷介导的熔化机制的涡旋晶格的熔化温度。