自旋注入有机物的扩散理论

根据自旋注入半导体的相关理论， 考虑到有机体内可能同时含有带自旋的单极化子和不带自旋的双极化子两种载流子，从扩散 理论和欧姆定律出发，建立了自旋注入有机体的唯象模型.通过计算发现，适当选择铁磁层极化率或两层的电导率可以使得有机层内电流具有高的自旋极化.进一步研究了单极化子浓度等因素对注入电流极化的影响. 关键词： 自旋电子学 自旋注入 有机聚合物 极化子     

一维铁磁/有机系统的基态与自旋分布研究

文中用一维紧束缚模型描述铁磁金属,用一维非简并的Su-Schrieffer -Heeger (SSH)模型描述共轭聚合物,研究了在一维铁磁/共轭聚合物系统和一维CMR材料/ 聚合物系统中的电子转移和自旋转移.发现在聚合物部分没有自旋的双极化子比有自旋的极化子具有较低的能量而容易产生.然而在铁磁CMR材料/聚合物系统中极化子的产生能低于聚合物中极化子的产生能,增加了有机物中自旋极化输运的可能性.     

极化子比率变化对自旋注入有机半导体性质的影响

从自旋扩散方程和欧姆定律出发研究了铁磁层到有机半导体的自旋注入,得到了系统的电流自旋极化率。有机半导体中的载流子为自旋极化子和不带自旋的双极化子,极化子比率在有机半导体内随输运距离变化。通过计算发现匹配的铁磁和有机半导体电导率有利于自旋注入;通过调节界面电阻自旋相关性,电流自旋极化率可获得很大程度提高;极化子比率衰减速率对有机半导体电流自旋极化率具有非常重要的影响。     

铁磁/有机半导体/铁磁系统的电流自旋极化性质研究

根据有机半导体中的电流自旋极化注入和输运实验现象，理论上研究了铁磁/有机半导体/铁磁系统的电流自旋极化性质.考虑到有机半导体的具体特性，从自旋扩散理论和欧姆定律出发，得到了系统的电流自旋极化率.假设自旋极化子和不带自旋的双极化子为有机半导体中的载流子.通过计算发现，极化子为实现有机半导体中电流极化注入和输运的有效自旋载流子，即使它只占总载流子很少一部分.还进一步研究了自旋相关界面电阻和电导率匹配以及有机半导体长度等因素对系统电流自旋极化的影响. 关键词： 自旋电子学 自旋注入 有机半导体 极化子     

有机器件电流自旋极化放大性质研究

基于自旋扩散漂移方程,考虑到电场的影响及有机半导体中特殊的载流子电荷自旋关系, 对一个简单的T型结构有机自旋器件模型进行了理论研究,得出了此有机器件的电流自旋 极化放大率表达式.研究表明,器件中极化子比率、电场和电流密度都会影响器件的电流 自旋极化放大率,通过调节此有机器件的电场和极化子比率可以获得较大的电流自旋 极化放大率.     

有机自旋器件磁性渗透层中双极化子对自旋极化输运的影响

根据实验发现的有机器件如Co/有机半导体/La_0.7Sr_0.3MnO₃中磁性原子渗透现象, 利用自旋漂移-扩散方程, 理论研究了磁性渗透层中极化子-双极化子的转化对自旋极化输运的影响. 研究发现: 磁性渗透层具有不同于纯净有机层的迁移率和自旋反转时间, 都将影响极化子-双极化子的转化, 进而影响自旋极化的输运; 在磁性渗透层中极化子自旋反转时间的劈裂是引起自旋弛豫的主要因素, 而极化子和双极化子之间的转化是重要因素.     

一维铁磁/有机共轭聚合物的自旋极化研究

针对最近关于自旋注入有机体的实验研究，理论上计算了有机分子与磁性原子接触时的自旋极化现象.通过调节磁性原子的自旋劈裂强度，发现有机分子链内的自旋极化弱于金属链，但强于半导体链.同时还研究了有机分子链内自旋极化随电子-声子耦合强度的变化关系以及界面耦合的自旋相关效应. 关键词： 界面耦合 自旋极化 自旋劈裂     

二维量子点中极化子的自旋弛豫

在考虑Rashba自旋-轨道耦合的条件下, 采用二次幺正变换和变分方法研究了二维抛物量子点中由于电子与体纵光学声子的耦合作用形成的极化子在基态Zeeman分裂能级上的自旋弛豫过程.这一过程主要是通过吸收或发射一个形变势或压电声学声子完成.具体分析了强、弱耦合两种极限下极化子自旋弛豫率与外磁场、量子点半径、Landau因子参数、Rashba自旋轨道耦合参数的变化关系. 关键词： 自旋弛豫 极化子 Rashba自旋轨道耦合 量子点     

电磁诱导光透明过程中两原子的自旋极化特性

本文研究了电磁诱导光透明过程中两原子的自旋极化矢量。对于数态探测场,在光信息转移过程中,两原子自旋极化矢量始终固定在z方向,大小变化非常明显,两原子一般处于混合态;对于相干态探测场,自旋极化矢量大小变化很微弱,两量子比特基本处于纯态,这有利于改善系综内原子之间的相干性,但自旋极化矢量的方向在x-z平面内。     

电磁诱导光透明过程中两原子的自旋极化特性

本文研究了电磁诱导光透明过程中两原子的自旋极化矢量.对于数态探测场,在光信息转移过程中,两原子自旋极化矢量始终固定在z方向,大小变化非常明显,两原子一般处于混合态;对于相干态探测场,自旋极化矢量大小变化很微弱,两量子比特基本处于纯态,这有利于改善系综内原子之间的相干性,但自旋极化矢量的方向在x-z平面内.     

Dynamics of polaron in a polymer chain with impurities

In a polymer chain, an extra electron or hole distorts the chain to form a charged polaron, which is the charge carrier being responsible for conductivity. When an intermediate-strength electric field is applied, the polaron will be accelerated for a short time and then move at a constant velocity. The dynamical process of polaron in a polymer chain with impurities is simulated within a non-adiabatic evolution method, in which the electron wave function is described by the time-dependent Schrödinger equation while the polymer lattice is treated classically by a Newtonian equation of motion. We have considered two kinds of dynamical processes, one is the field-induced depinning of a charged polaron, which is initially bound by an attractive impurity; and the other is the scattering of a polaron from an impurity. In the former process, the charged polaron will depart from the attractive impurity only for the applied field with strength over a threshold, otherwise, the polaron will oscillate around the impurity. In the latter process, the charged polaron moves through the impurity in the presence of an electric field while it will be bounced back for a repulsive impurity or trapped to oscillate around an attractive impurity in the case that the applied electric field is weak and just be present for the polaron acceleration.Received: 4 June 2004, Published online: 14 December 2004PACS: 71.38.-k Polarons and electron-phonon interactions - 72.80.Le Polymers; organic compounds (including organic semiconductors)     

共轭高分子链中电荷迁移的热效应

从理论上研究了共轭高聚物链中在电场作用下极化子运动的热效应.基于SSH模型以及通过绝热动力学演化的方法,模拟了共轭高聚物链中极化子在电场作用下从链左端向右端运动的过程.晶格受到的热扰动作用假设为通过局域的晶格范围内原子位移的随机涨落来实现.结果发现,晶格中的局域热涨落对于运动中的极化子而言等效于一个势垒.势垒高度由高分子中受到热扰动的区域的范围大小以及该区域与其周围环境的温差来决定.当分子中存在热吸收不均匀的现象时,链内极化子迁移率在低电场范围内随电场的变化遵循对数曲线变化规律.     

Polaron dynamics in a system of coupled conjugated polymer chains

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.     

共轭高聚物链中极化子生成的掺杂效应

在紧束缚近似下,用绝热动力学演化的方法研究了共轭高聚物链中低浓度掺杂对极化子生成位置的影响。研究发现,掺入杂质与注入电子的先后次序不同,极化子生成的位置会有很大差别,先注入电子后掺入杂质的情况下,在链端自由区与过渡区,极化子生成位置受杂质影响较小;而先杂质后电子的次序下,极化子的生成位置明显受到杂质的控制。该研究表明共轭高聚物链中极化子的生成位置可通过调节掺杂与电荷注入的次序加以控制,从而可达到间接改变载流子迁移率的目的。     

共轭高聚物中极化子散射引起的激子迁移(英文)

基于Su-Schrieffer-Heeger(SSH)模型并考虑到Brazovskii-Kirova对称破缺项,研究了共轭聚合物中注入极化子和激子在外电场下的散射过程.研究发现在外场作用下极化子总是能通过激子,而激子的运动行为则密切依赖于电场的强度.如果电场大于临界电场3.0×10~5V/cm,那么激子与极化子散射后并不发生任何运动;然而当电场小于此临界值时,激子将在极化子运动的相反方向上有一个明显的位移.激子在弱电场下所发生的这种迁移运动,是由于同极化子发生了慢散射作用.     

Dynamics of Polaron at Polymer/Polymer Interface

The migration of a polaron at polymer/polymer interface is believed to be of fundamental importance for the transport and light-emitting properties of conjugated polymer-based light emitting diodes. Based on the one- dimensional tight-binding Su-Schrieffer-Heeger （SSH） model, we have investigated polaron dynamics in a one- dimensional polymer/polymer system by using a nonadiabatic evolution method. In particular, we focus on how a polaron migrates through the conjugated polymer/polymer interface in the presence of external electric field. The results show that the migration of polaron at the interface depends sensitively on the hopping integrals, the potential barrier induced by the energy mismatch, and the strength of applied electric field which increases the polaron kinetic energy.     

杂质离子对有机共轭聚合物中极化子动力学性质的影响

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.     

共轭高分子链中大极化子与小极化子的弹性碰撞

基于Su-Schrieffer-Heeger(SSH)模型,考虑电子-电子相互作用,以及在哈密顿量中引入Brazovskii-Kivova对称破缺项,采用动力学演化的方法研究了在外电场作用下共轭高聚物分子链中大极化子与小极化子之间的弹性散射过程.研究发现,载流子的载荷性质不但决定大小极化子之间的相互作用性质,也深刻地影响了其发生散射后的载流子输运性质.在较低电场的作用下,当两载流子电性相同时,发生碰撞后,小极化子将推动着大极化子一起运动;而当两者电性相反时,碰撞后,大极化子将拖曳着小极化子一起运动.当电场强度超过临界值时,将产生量子隧穿效应,即,大小极化子相互迅速穿透,且不受载流子的载荷影响.     

Spin charge carrier dynamics in poly(bis-alkylthioacetylene)

Initial and laser-irradiated poly(bis-alkylthioacetylene) (PATAC) samples were investigated by electron paramagnetic resonance (EPR) at X-band (9.6 GHz), Q-band (37 GHz), and D-band (140 GHz) in a wide temperature range. Two types of paramagnetic centers were proved to exist in laser-modified polymer, namely, localized and mobile polarons with the concentration ratio and susceptibility depending on the irradiation dose and temperature. Superslow torsion motion of the polymer chains was studied by the saturation transfer method at D-band EPR. Additional information on the polymer chain segment dynamics was obtained by the spin probe method at X-band EPR. Spin-spin and spin-lattice relaxation times were measured separately by the steady-state saturation method at D-band EPR. Intrachain and interchain spin diffusion coefficients and conductivity arising from the polaron dynamics were calculated. It was shown that the polaron dynamics in laser-modified polymer is affected by the spin-spin interaction. The interchain charge transfer is stimulated by torsion motion of the polymer chains, whereas the total conductivity of irradiated PATAC is determined mainly by the dynamic of diamagnetic charge carriers. Magnetic, relaxation and dynamics parameters of PATAC were also shown to change during polymer storage.     

Combined polarons in a pernigraniline-base polymer

We found a ring-torsin polaron which is associated with a bond-order polaron in a pernigraniline-base polymer on the basis of the extended Ginder-Epstein model. The calculated electronic structure for a n-type polaron has shown that the transition from the lower gap level to the higher one matched the 1.5 eV peak of photoinduced absorption in the polymer. The origin of the large defect mass is suggested.