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本文讨论极性晶体中慢激子极化势的性质,把作者过去的工作推广到电子和空穴质量不相等的情形。采用微扰法,在忽略反冲效应中不同波矢的声子之间的相互作用后,计算了二级近似的波函数。由此进一步计算了慢激子的极化电势,发现:激子的极化电势受到纵光学声子的屏蔽,其屏蔽长度与纵光学声子的频率、激子的质量的平方根成反比;极化电势和电子、空穴质量有关,在电子、空穴质量比等于1时最小。
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自从发观半导体激光以后,对强激发半导体辐射过程已经有了广泛的研究。事实上,可以遇到完全不同的情况,这取决于不同的电子空穴对的激发密度和温度。仅只考虑本征效应,就能区别下列状态: 1)在中等密度和温度下,观察到弱相互作用的粒子气(激子、电子……),在那里新的辐射过程促成两个激发的碰撞(激子——激子,激子——电子)。 2)在非常高的密度下,该系统作为简 相似文献
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在本文中用Haga研究极化子时提出的微扰法讨论晶格振动对激子运动的影响。把作者过去的工作推广到电子和空穴质量不相等的普遍情形。在忽略反冲效应中不同波矢的声子之间的相互作用时,导出了激子的基态能量、有效质量、约化质量和内部势能。指出:激子的有效质量和电子、空穴与声子的相互作用有关;激子的约化质量不仅和电子、空穴与声子的相互作用有关,而且还和电子空穴质量比有关;激子形成自陷态的条件并非由电子、空穴与声子相互作用的大小,而是由电子、空穴质量比决定。形成激子自陷的条件是电子、空穴质量比0.261<μe/μh<3.83。在μe/μh<0.261或μe/μh>3.83的情形,激子极化晶体中并不形成自陷态。
关键词: 相似文献
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自旋是基本粒子(电子、光子)角动量的内在形式.固体中体现自旋特征的集体电子行为如拓扑绝缘体等是当前凝聚态物理领域关注的焦点,是基态行为.激子作为电子空穴对的激发态且寿命很短,可复合发光,它是否能体现自旋极化主导的行为?对此人们的认识远不如针对基态的电子.激子磁极化子(exciton magnetic polaron, EMP)是由磁性半导体微结构中铁磁自旋耦合态与自由激子相互作用形成的复合元激发,但其研究很有限.本文概述了我们在稀磁半导体微纳米结构中的EMP及其发光动态学光谱、自旋极化激子凝聚态的形成方面取得的一些进展,展望了未来可能在自旋光电子器件、磁控激光、光致磁性等量子技术方面的潜在应用. 相似文献
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自旋是基本粒子(电子、光子)角动量的内在形式.固体中体现自旋特征的集体电子行为如拓扑绝缘体等是当前凝聚态物理领域关注的焦点,是基态行为.激子作为电子空穴对的激发态且寿命很短,可复合发光,它是否能体现自旋极化主导的行为?对此人们的认识远不如针对基态的电子.激子磁极化子(exciton magnetic polaron,EMP)是由磁性半导体微结构中铁磁自旋耦合态与自由激子相互作用形成的复合元激发,但其研究很有限.本文概述了我们在稀磁半导体微纳米结构中的EMP及其发光动态学光谱、自旋极化激子凝聚态的形成方面取得的一些进展,展望了未来可能在自旋光电子器件、磁控激光、光致磁性等量子技术方面的潜在应用. 相似文献
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We present measurements and simulations of coherent control and readout of the polarization in individual exciton states. The readout is accomplished by transient four-wave mixing detected by heterodyne spectral interferometry. We observe Rabi oscillations in the polarization, which show half the period of the Rabi oscillations in the population. A decrease of the oscillation amplitude with pulse area is observed, which is not accompanied by a change in the dephasing time. This suggests the transfer of the excitation to other states as the origin of the Rabi-oscillation damping. Detuning of the excitation enables the control of the polarization in phase and amplitude and is in qualitative agreement with simulations for a two-level system. Additionally, simultaneous Rabi flopping of several spatially and energetically close exciton states is demonstrated. 相似文献
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The evolution of an electromagnetic wave with slowly varying polarization, which interacts resonantly with the medium formed by degenerate two-level atoms, is studied using the wave function approach under the conditions of electromagnetically induced transparency. It is shown that the amplitude of the wave field propagates at the velocity of light in such a medium. The equation obtained for the polarization parameter has a solution in the form of a simple wave. The breaking length is determined. It is shown that the velocity of propagation of polarization waves may be much smaller than the velocity of light. The proposed approach is common for two-level systems with an arbitrary degeneracy. The case of a system with Zeeman degeneracy is analyzed in detail. The dependence of the velocity of propagation of the polarization structure on the amplitude and polarization is determined for an arbitrary level degeneracy. The evolution of the polarization structure in such a medium is discussed. 相似文献
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分子的激发能量转移和电荷转移是提高光伏电池和发光二极管效率的关键问题,其中分子聚集体中的激子-激子湮灭过程是影响分子激发能量转移的重要方面,细致研究激子-激子湮灭的动力学过程并与相关的瞬间吸收谱信号对比对相关的理论和实验都有重要意义.本文在分子间弱耦合近似下,用经典的率方程,应用方酸分子的基本参数对激子-激子湮灭过程做了微观描述,通过改变相关参数,研究了外场激发强度、聚集体的偶极矩位形、分子内的衰变率等因素对激子-激子湮灭过程的影响,分析了激子在第一激发态和高阶激发态的驰豫时间、电荷转移相干时间、激子融合和湮灭时间之间的关系,得到的结论适用于高阶激发态能级能量约为第一激发态能级能量的2倍的分子组成的分子聚集体.研究发现,J型聚集体由于相干能量转移时间较短,比H型聚集体有更高的湮灭率.激发场强越强,激子-激子湮灭的效率越高.分子高阶激发态的衰变率是激子-激子湮灭过程的关键因素. 相似文献
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This article presents a comprehensive many-body theory for
optically excited semiconductors. The coupled equations
of motion for the correlation functions of the
Coulomb-interacting electron-hole system are derived
and solved for different excitation conditions. The generation of a
coherent excitonic polarization and its conversion into
incoherent populations is analyzed.
The spontaneous emission properties of the excited
system are evaluated using a fully quantized theory.
Luminescence from excitonic and electron-hole plasma
populations is computed, and significant hole burning in
the exciton center of mass distributions is predicted.
It is shown how different
excitations states of the many-body system
can be identified by their
characteristic signatures in the absorption spectra of a terahertz probe field. 相似文献
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A. I. Maĭmistov 《Optics and Spectroscopy》2002,93(1):45-51
The propagation of ultrashort optical pulses in a chain of two-level two-electron quantum dots was studied theoretically. It was assumed that an excited state of an individual quantum dot can be transferred to the neighboring quantum dots, as is the case for a molecular exciton. As a result, optical-pulse motion is accompanied with a wave of polarization of quantum dots. It is shown that two types of steady-state circularly polarized solitary polaritonic waves can propagate along such chains; these are waves with exponentially and algebraically decaying leading and trailing edges. 相似文献
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寻找新光源, 特别是短波长相干光源备受关注. 本文讨论了晶体摆动场辐射作为短波长激光的可能性和必须满足的基本条件; 指出了至今尚未获得可利用的短波长激光可能不只是技术原因, 而且还有物理原因. 利用参数激励方法对这个问题进行了分析. 在经典力学框架内和偶极近似下, 引入正弦平方势, 把粒子运动方程化为具有阻尼项和参数激励项的摆方程. 利用Melnikov方法讨论了系统的稳定性, 并对系统的临界条件进行了分析. 结果表明: 系统的稳定性与其参数有关, 只需适当调节这些参数, 系统的稳定性就可以原则上得到保证.
关键词:
晶体摆动场辐射
沟道辐射
参数激励
稳定性 相似文献