共查询到18条相似文献,搜索用时 187 毫秒
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采用拓展紧束缚Su-Schrieffer-Heeger(SSH)模型,研究了链间耦合对反式聚乙炔多链体系中电子极化子再激发态的晶格位形、净电荷密度、局域能级波函数和态密度的影响.结果发现:对于两条链体系,当链间耦合很小(t⊥≤0.01 e V)时,注入到系统中的电子只会在第一条链上诱发产生一个晶格缺陷,形成电子极化子再激发态,这和单链体系是一致,而第二条链仍是二聚化基态.随着链间耦合的增大,第一条链上缺陷的局域度减少而第二条链上的缺陷局域度相应增加,直至两条链上的位形相同;对于多条链(5条链和6条链)体系,当耦合很小(t⊥≤0.05 e V)时,电子极化子再激发态也只会存在于一条链上,当链间耦合较强时,极化子再激发态会在链间层次性地扩展开来,并不会出现多条链位形相同;从两条链的能级图上可以看到随着链间耦合t⊥的增大,体系的带隙不断的增大和电子态密度显示的是完全吻合的,体系的导电性减弱.通过分析两条链体系在t⊥=0 e V和t⊥=0.1 e V的能级态密度,发现链间耦合越强,则中间局域能级的态密度越小,最后没有中间局域态. 相似文献
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从拓展紧束缚模型出发,研究了链间耦合对反式聚乙炔多链体系中电子极化子再激发态的晶格位形、净电荷密度、局域能级波函数和态密度的影响。结果发现:对于两条链体系,当链间耦合很小(eV)时,注入到系统中的电子只会在第一条链上诱发产生一个晶格缺陷,形成电子极化子再激发态,这和单链体系是一致,而第二条链仍是二聚化基态。随着链间耦合的增大,第一条链上缺陷的局域度减少而第二条链上的缺陷局域度相应增加,直至两条链上的位形相同。对于多条链(5条链和6条链)体系,当耦合很小(0.05eV)时,电子极化子再激发态也只会存在于一条链上,当链间耦合较强时,极化子再激发态会在链间层次性地扩展开来,并不会出现多条链位形相同。从两条链的能级图上可以看到随着链间耦合的增大,体系的带隙不断的增大和电子态密度显示的是完全吻合的,体系的导电性减弱。通过分析两条链体系在eV和eV的能级态密度,发现链间耦合越强,则中间局域能级的态密度越小,最后没有中间局域态。 相似文献
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苯环取代聚乙炔是一类具有简并基态的发光聚合物.利用扩展的SuSchriefferHeeger模型,研究了这类聚合物链中的孤子、极化子等元激发特性.结果表明:由于苯环与聚乙炔主链间的强π电子耦合,苯环取代抑制了聚乙炔主链的二聚化,减小了导带与价带之间的能隙;因此取代聚乙炔中的元激发具有较小的激发能,同时具有更大的相干长度.尽管苯基取代对元激发有很大的影响,但是非取代聚乙炔中元激发的基本物理规律依然成立,表明这些元激发的基本特性不受取代基团的影响
关键词:
孤子
极化子
苯基取代聚乙炔 相似文献
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邱宇 《原子与分子物理学报》2020,37(4):483-486
有机共轭高分子中,孤子、极化子及激子都是基本的元激发,对解释有机聚合材料的导电发光特性起着主导作用.孤子、极化子以及激子等在晶格位形上都是各具特征的空间局域状态.本文将讨论在有机共轭高分子中存在着另一种局域态——链间耦合局域态,这种局域态是由于分子链间的相互作用所导致,在相互作用分子链端附近形成势阱,可有效束缚电子和空穴等带电粒子. 相似文献
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自陷电子对了解光电材料的光学性质非常重要.近些年来,形变晶格中电子自陷的问题受到研究人员的广泛关注.电子既与声学模耦合,也与光学模相互作用,但电子由自由态向自陷态的转变缘于近程的电子-声学声子耦合.研究表明:声学极化子在大多数半导体以及Ⅲ-Ⅴ族化合物,甚至碱卤化物中都不可能自陷.另一方面,电子-声子耦合在束缚结构,如二维、一维系统中,会有所增强.换言之,电子在低维结构中更容易自陷.Farias等人指出:声学极化子在二维系统中自陷的临界电子-声子耦合常数为定值,不随声子截止波矢的变化而改变.这种结论在物理上不尽合理.通过计算二维系统中的声学极化子基态能量和有效质量,讨论了二维声学极化子自陷问题.研究发现,二维声学极化子自陷转变的临界耦合常数随声子截止波矢的增加朝电子-声子耦合较弱的方向变化.这一特征与前人关于体和表面极化子研究获得的结论定性一致.所得二维声学极化子基态能量的表达式与Farias等人一致,但自陷的结果与Farias等人的结果在定性和定量上均有不同,我们认为Farias等人关于二维声学极化子自陷转变点的确定方式有不妥之处.通过改进自陷转变点的确定方式,得到了在物理上更合理的结果. 相似文献
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LIU Wen GAO Kun LI Yuan SUN Zhen & LIU DeSheng School of Physics Sh ong University Jinan China 《中国科学:物理学 力学 天文学(英文版)》2010,(2)
Polaron dynamics in a system of highly ordered conjugated polymer chains is investigated based on the tight binding model. With the interchain coupling enhancing,it takes longer time for the electron added to the system to induce a localized polaron state. Beyond a certain strength of the interchain coupling,the electron evolves into a two-dimensional delocalized polaron state. Dynamical simulations suggest that the well-ordered organic molecule systems with two-dimensional polarons exhibit higher mobilitie... 相似文献
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Z. An B. Di H. Zhao C. Q. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):71-77
Within an one-dimensional tight-binding model, we
investigate the inelastic scattering processes of oppositely
charged polarons in conjugated polymers under the influence of an
external electric field, by using a nonadiabatic evolution method.
It is found that the polaron pair does not necessarily scatter
into an entity(neutral exciton), but a mixed state composed of
both polarons and excitons. The yield of the neutral exciton
depends sensitively on the strength of applied fields.
Additionally, effects of interchain coupling on the scattering
processes are also discussed, which shows that the interchain
coupling is of fundamental importance and facilitates the
formation of the polaron-exciton. 相似文献
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The motion of excitations such as polarons is believed to be of fundamental importance for the transport properties of conjugated polymers for the use in, e.g., polymer based LED's. We have investigated polaron dynamics in a system of coupled polymer chains in the presence of an external electric field. In particular, we focus on how a polaron migrates through the polymer lattice, i.e., the situation in which a polaron reaches a chain end and is scattered to the surrounding chains. We show that the outcome of this event strongly depends on the strength of the electric field, and we identify three different cases for the polaron migration. 相似文献
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文中模拟了在基态非简并聚合物中的极化子和双极化子在弱电场中的运动,研究了在不同简并参数的系统中极化子和双极化子的动力学稳定性,发现在同一个系统中,双极化子比极化子的运动速度慢,晶格振荡小; 在简并参数大的系统中,极化子和双极化子的运动速度都变慢.极化子和双极化子在弱电场下都存在饱和速度,达到饱和速度后, 电场的能量发生了转换. 相似文献
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We report the direct time domain observation of a many-body process in a two-dimensional system: small polaron formation from the localization of a conduction band electron in NaCl thin films of unit cell thickness. Contrary to theoretical prediction for bulk NaCl crystal where an electron polaron does not exist, time-resolved two-photon photoemission reveals small polaron formation from delocalized conduction band electrons in crystalline NaCl thin films. The increased deformability and the reduced electronic bandwidth of a crystalline lattice in the thin film format are both responsible for the formation of small polarons that are absent in bulk solids. 相似文献
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V. K. Mukhomorov 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):19-23
It is established, that action of intense laser field results in occurrence
of two equivalent positions of a large polaron localization. This paper
analyzes the tunneling oscillations of polarons about its equilibrium
positions and the interaction between polarons in quasi two-dimensional
dielectric layers. It is shown that oscillations of polarons in intense
laser field lead to effective interpolaron attraction in coordinate space.
This effect promotes Bose-Einstein condensation of bipolarons and to emerge
of high-temperature superconductivity. 相似文献
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基于一维紧束缚Su-Schrieffer-Heeger模型, 采用分子动力学方法, 讨论了杂质势的强度和杂质之间的距离对电子和空穴极化子动力学性质的影响. 研究结果表明: 1)当杂质势强度保持不变时, 两杂质离子之间的距离(d)在2-16个晶格常数变化时, 电子极化子的平均速度大于空穴极化子的平均速度, 这是由于电子、空穴极化子与杂质势的库仑作用不同而产生的差异, 同时极化子的平均速度随d的增加而增大; 若继续增加杂质离子之间的距离, 电子和空穴极化子的平均速度几乎保持不变, 仅有一些微小的振荡, 这是由于不同距离的杂质离子对电子和空穴极化子产生的势垒或势阱的叠加效果不同而引起的; 2)保持两杂质离子之间的距离不变时, 随着杂质势强度的增大, 电子和空穴极化子的平均速度均减小, 且空穴极化子的平均速度减小趋势更明显. 相似文献
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Jingxi Luo Bernard M. A. G. Piette 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(8):155
We present a one-parameter family of mathematical models describing the dynamics of polarons in periodic structures, such as linear polypeptides, which, by tuning the model parameter, can be reduced to the Davydov or the Scott model. We describe the physical significance of this parameter and, in the continuum limit, we derive analytical solutions which represent stationary polarons. On a discrete lattice, we compute stationary polaron solutions numerically. We investigate polaron propagation induced by several external forcing mechanisms. We show that an electric field consisting of a constant and a periodic component can induce polaron motion with minimal energy loss. We also show that thermal fluctuations can facilitate the onset of polaron motion. Finally, we discuss the bio-physical implications of our results. 相似文献