共查询到17条相似文献，搜索用时 46 毫秒
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研究了外场驱动下非对称耦合量子点分子中激子的动力学行为.利用二能级理论分析了这个量子系统中激子的局域化现象,分析发现:激子的动力学行为主要发生在低能级子空间,它们构成了系统的两个局域态;当场强和频率是Bessel方程的根时,准能发生回避交叉,局域化现象发生,电子和空穴局域在初始状态,状态不随时间变化.数值计算也证明了这一点.同时还给出了电子和空穴的最大纠缠态随时间的演化. 相似文献
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利用两点Hubburd模型和Floquet理论,用数值方法求解了含时Sch(o)dinger方程,给出了电子-空穴局域于初始态的几率在20个驱动周期内的最小值,研究了在直流和交流电场驱动下耦合双量子点分子中激子的动力学行为.结果表明,在弱场情况下,激子主要在局域态之间隧穿;在强场情况下,电子和空穴可以独立地在量子点间隧穿.驱动场倾向于使电子和空穴在空间分离,但在合适的条件下量子点中的电子和空穴在短时间内仍可以保持在初始局域态.直流电压破坏系统的动力学对称性,并对动态局域化产生影响. 相似文献
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利用两点Hubburd模型和Floquet理论,用数值方法求解了含时Sch(o)dinger方程,给出了电子-空穴局域于初始态的几率在20个驱动周期内的最小值,研究了在直流和交流电场驱动下耦合双量子点分子中激子的动力学行为.结果表明,在弱场情况下,激子主要在局域态之间隧穿;在强场情况下,电子和空穴可以独立地在量子点间隧穿.驱动场倾向于使电子和空穴在空间分离,但在合适的条件下量子点中的电子和空穴在短时间内仍可以保持在初始局域态.直流电压破坏系统的动力学对称性,并对动态局域化产生影响. 相似文献
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采用两点Hubbard模型和Floquet定理研究了在交变电场驱动下双量子点分子中激子的动力学行为.数值计算表明,系统准能随交变电场振幅的变化会出现一系列严格交叉和回避交叉.在某些弱场区的准能交叉点处,初始局域在一个量子点的电子和空穴依旧保持其初始局域状态.特别是随着两粒子之间的库仑相互作用的增强,这种动态局域化程度也得到加强.在强场区准能交叉点处,激子的动态局域化也能够建立起来.应用微扰理论求解Floquet方程,得到准能的解析解,可更清晰地了解系统的这种动态局域化特性. 相似文献
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双量子点分子中激子的动态局域化行为 总被引：2，自引：2，他引：0
采用两点Hubbard模型和Floquet定理研究了在交变电场驱动下双量子点分子中激子的动力学行为.数值计算表明,系统准能随交变电场振幅的变化会出现一系列严格交叉和回避交叉.在某些弱场区的准能交叉点处,初始局域在一个量子点的电子和空穴依旧保持其初始局域状态.特别是随着两粒子之间的库仑相互作用的增强,这种动态局域化程度也得到加强.在强场区准能交叉点处,激子的动态局域化也能够建立起来.应用微扰理论求解Floquet方程,得到准能的解析解,可更清晰地了解系统的这种动态局域化特性 相似文献
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利用有效的两点Hubbard模型,研究了在高强度交变电场驱动下的双量子点分子中激子的动力学行为．利用微扰理论,求解Floquet方程,从而得到准能的解析解,表明准能随交变电场的变化出现一系列共振点．通过计算初始局域态随时间的演化,发现在这些共振点处,动态局域化能够建立起来,说明尽管驱动电场倾向于使电子和空穴在空间分离,但在合适的强外电场驱动与弱的量子点间的耦合作用下,初始局域态依旧可保持动态局域化． 相似文献
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半导体量子点中强耦合激子的性质 总被引：2，自引：0，他引：2
研究了抛物型半导体量子点中强耦合激子的性质.在有效质量近似下,采用线性组合算符和幺正变换的方法,导出了半导体量子点中重空穴激子的基态能量.在强耦合情况下讨论了量子点半径和受限强度对半导体量子点中激子基态能量的影响.以氯化铊(TlCl)半导体为例进行了数值计算.结果表明:在强耦合情况下,重空穴激子的基态能量随量子点半径的增大而减小,随量子点受限强度的增大而增大. 相似文献
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Y. H. Chang M. H. Chieng C. C. Tsai M. C. Harris Liao Y. F. Chen 《Journal of Electronic Materials》2000,29(1):173-176
We report detailed photoluminescence (PL) studies of ZnSe quantum dots grown by controlling the flow duration of the precursors
in a metal-organic chemical vapor deposition system. The growth time of the quantum dots determines the amount of blue shift
observed in the PL measurements. Blue shift as large as 320 meV was observed, and the emission was found to persist up to
room temperature. It is found that changing the flow rate and the total number of quantum dot layers also affect the peak
PL energy. The temperature dependence of the peak PL energy follows the Varshni relation. From analyzing the temperature-dependent
integrated intensity of the photoluminescence spectra, it is found that the activation energy for the quenching of photoluminescence
increases with decreasing quantum dot size, and is identified as the binding energy of the exciton in ZnSe quantum dot. 相似文献
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Kiran Lingam Ramakrishna Podila Haijun Qian Steven Serkiz Apparao M. Rao 《Advanced functional materials》2013,23(40):5062-5065
For a practical realization of graphene‐based logic devices, the opening of a band gap in graphene is crucial and has proven challenging. To this end, several synthesis techniques, including unzipping of carbon nanotubes, chemical vapor deposition, and other bottom‐up fabrication techniques have been pursued for the bulk production of graphene nanoribbons (GNRs) and graphene quantum dots (GQDs). However, only limited progress has been made towards a fundamental understanding of the origin of strong photoluminescence (PL) in GQDs. Here, it is experimentally shown that the PL is independent of the functionalization scheme of the GQDs. Following a series of annealing experiments designed to passivate the free edges, the PL in GQDs originates from edge‐states, and an edge‐passivation subsequent to synthesis quenches the PL. The results of PL studies of GNRs and carbon nano‐onions are shown to be consistent with PL being generated at the edge sites of GQDs. 相似文献
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Jung-Yao Chen Dong-Lin Yang Fu-Cheng Jhuang Yu-Han Fang Jean-Sebastien Benas Fang-Cheng Liang Chi-Ching Kuo 《Advanced functional materials》2021,31(47):2105911
Emulation of photonic synapses through photo-recordable devices has aroused tremendous discussion owing to the low energy consumption, high parallel, and fault-tolerance in artificial neuromorphic networks. Nonvolatile flash-type photomemory with short photo-programming time, long-term storage, and linear plasticity becomes the most promising candidate. Nevertheless, the systematic studies of mechanism behind the charge transfer process in photomemory are limited. Herein, the physical properties of APbBr3 perovskite quantum dots (PQDs) on the photoresponsive characteristics of derived poly(3-hexylthiophene-2,5-diyl) (P3HT)/PQDs-based photomemory t hrough facile A-site substitution approach are explored. Benefitting from the lowest valance band maximum and longest exciton lifetime of FAPbBr3 quantum dot (FA-QDs), P3HT/FA-QDs-derived photomemory not only exhibits shortest photoresponsive characteristic time compared to FA0.5Cs0.5PbBr3 quantum dots (Mix-QDs) and CsPbBr3 quantum dots (Cs-QDs) but also displays excellent ON/OFF current ratio of 2.2 upon an extremely short illumination duration of 1 ms. Moreover, the device not only achieves linear plasticity of synapses by optical potentiation and electric depression, but also successfully emulates the features of photon synaptic such as pair-pulse facilitation, long-term plasticity, and multiple spike-dependent plasticity and exhibits extremely low energy consumption of 3 × 10−17 J per synaptic event. 相似文献
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耦合GaN/AlxGa1-xN量子点的非线性光学性质 总被引：1，自引：1，他引：0
在有效质量和偶极矩近似下,考虑了由于压电极化和自发极化所引起的内建电场和量子点的三维约束效应,对纤锌矿对称Al_xGa_(1-x)N/GaN/Al_xGa_(1-x)N/GaN/Al_xGa_(1-x)N圆柱型应变耦合量子点中激子非线性光学性质进行了研究。计算结果表明,内建电场使吸收光谱向低能方向移动,发生红移现象,并且使吸收峰强度大大减小。量子限制效应使光吸收峰强度随着量子点尺寸的减小而增强,并且随着量子点尺寸的减小,吸收光谱发生蓝移现象。 相似文献
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Rigorous and intuitive master equation models are presented to study on‐demand single photon sources from pulse‐excited quantum dots coupled to optical cavities. Three methods of source excitation are considered: resonant pi‐pulse, off‐resonant phonon‐assisted inversion, and two‐photon excitation of a biexciton–exciton cascade, and the effect of the pulse excitation process on the quantum indistinguishability, efficiency, and purity of emitted photons is investigated. By explicitly modelling the time‐dependent pulsed excitation process in a manner which captures non‐Markovian effects associated with coupling to photon and phonon reservoirs, it is found that photons of near‐unity indistinguishability can be emitted with over 90% efficiency for all these schemes, with the off‐resonant schemes not necessarily requiring polarization filtering due to the frequency separation of the excitation pulse, and allowing for very high single photon purities. Furthermore, the off‐resonant methods are shown to be robust over certain parameter regimes, with less stringent requirements on the excitation pulse duration in particular. Also, a semi‐analytical simplification of the master equation is derived for the off‐resonant drive, which gives insight into the important role that exciton–phonon decoupling for a strong drive plays in the off‐resonant phonon‐assisted inversion process. 相似文献
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