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1.
Effect of temperature on the polaron stability in a one-dimensional organic lattice is investigated within the Su-Schrieffer-Heeger model. The temperature effect is simulated by introducing random forces to the equation of the lattice motion. It is found that the localized polaron state becomes delocalized even at low temperatures. The time of polaron keeping localized depends on the magnitude of temperatures. By taking into account the thermal effect, we find that the dissociation field is weaker as compared with earlier works. 相似文献
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Y. H. Yan Z. An C. Q. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,42(2):157-163
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) 相似文献
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V. D. Lakhno A. N. Korshunova 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(2):147-151
A charge motion in an electric field in a Holstein molecular chain is modeled in the absence of dissipation. It is shown that
in a weak electric field a Holstein polaron moves uniformly experiencing small oscillations of its shape. These oscillations
are associated with the chain’s discreteness and caused by the presence of Peierls-Nabarro potential there. The critical value
of the electric field intensity at which the moving polaron starts oscillating at Bloch frequency is found. It is shown that
the polaron can demonstrate Bloch oscillations retaining its shape. It is also shown that a breathing mode of Bloch oscillations
can arise. In all cases the polaron motion along the chain is infinite. 相似文献
5.
We study the stationary motion of a polaron in a conducting polymer in the presence of a high electric field. Using the Su-Schrieffer-Heeger model plus an electric field, we find that at polaron velocities not exceeding the sound velocity, the dissipation of the electronic energy into the lattice occurs via emission of phonons with single selected wave vector. For this case the corresponding contribution to the polaron mobility can be calculated analytically. We discuss the issue of the polaron stability with respect to dissociation in a very high field at supersonic velocities. 相似文献
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使用正则变换方法,考察了一维Holstein极化子能带和有效质量的温度依赖性。结果表明,对于一定的电子声子耦合强度,Holstein极化子能带宽度随温度升高而变窄,有效质量随温度升高而增大。特别是当电子声子耦合强度足够大时,极化子能带宽度在很小的温度范围内会迅速地变为零,我们认为这种情况实际上是极化子从能带状态向自陷局域态的迅速转变,这与通常的相变现象有点相类似。当电子声子耦合常数越大时,极化子有效质量随温度的升高而增加得越快。很显然,研究电子声子相互作用,对理解固体的光学和输运等性质将有重要的意义。 相似文献
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We have studied the electric-field-driven motion of a polaron by solving the
time-dependent Schr\"{o}dinger equation nonadiabatically and the lattice
equation of motion simultaneously. It is found that the polaron may
experience two sequent transitions under high fields; one is the
transition from the subsonic to the supersonic state, and the other from the
supersonic to dissociated state. The acoustic mode is decoupled from the
charge when the polaron moves at a speed faster than the sound speed, and
then the optical mode is decoupled at the second transition to make the
polaron dissociate completely. 相似文献
9.
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. 相似文献
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本文模拟了基态非简并聚合物中的极化子和双极化子在强电场中的运动 ,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,发现在强场下简并参数对极化子的稳定性影响不大,极化子晶格畸变的运动滞后于电子的运动,价带上的电子在强电场的激发下参与导电.双极化子在简并参数大的系统中较为稳定. 相似文献
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《Superlattices and Microstructures》2005,37(1):43-53
We study theoretically the interaction between excitons and longitudinal optical (LO) phonons in a cylindrical disk-like semiconductor quantum dot under an applied magnetic field. Due to the intensity of the interaction in the strong coupling regime, a composite quasi-particle called exciton–polaron is formed. We focus on the effect of the disk size and an external magnetic field on the exciton–phonon interaction energy and the exciton–polaron modes. The numerical computation for a CdSe quantum disk have shown that the exciton–phonon interaction energy is very significant and is even dominant when the disk height is small, which leads to a large Rabi splitting between the exciton–polaron modes. We investigate also the effect of the temperature on the integrated photoluminescence (PL) intensity, and show that at relatively high temperature the LO phonons have a noticeable effect on it. This physical parameter also shows a great dependence on quantum disk size and on magnetic field. 相似文献
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A. L. Vartanian 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(4):481-486
The effect of an electric field on the basic parameters of confined and interfacepolarons in cylindrical nanowires embedded in a non-polar matrix are studied theoreticallyfor the first time. By using the Lee, Low, and Pines variational method, the analyticalexpressions for the quasi-one-dimensional Fröhlich polaron self-energy and effective massare obtained as functions of the wire radius and the strength of the electric fieldapplied perpendicular to the wire axis. We have shown that the polaron self-energy as wellas effective mass strongly depents on both the strengths of the electric field and on thewire radius. This will be taken into account in the interpretation of optical phenomenarelated to polaron motion in cylindrical nanowire, when the effect of an applied electricfield competes with the spatial quantum confinement. 相似文献
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A. Harhira L. Guilbert P. Bourson H. Rinnert 《Applied physics. B, Lasers and optics》2008,92(4):555-561
Photoluminescence related to the bound polaron NbLi4+ is investigated as a function of temperature and incident light intensity in iron-doped lithium niobate crystals with various
iron concentrations. Experiments are done under constant-wave (CW) and pulsed illumination. Its found that the decay time
is always monoexponential. The radiative lifetime, the activation energy of the nonradiative lifetime and the quenching temperature
are only weakly sensitive to iron concentration. On the other hand, the magnitude of the photoluminescence signal seems strongly
correlated to the Fe2+ concentration, and the superlinear regime evidenced at low CW illumination definitely confirms that polaron excitation in
lithium niobate is a two-step process. 相似文献
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The results reported recently concerning the phase transition of a polaron in a high magnetic field at zero temperature are generalized to arbitrary temperature. An experiment to observe this polaron phase-transition is suggested and the relevant parameters are given for sixteen compound semiconductors. 相似文献
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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. 相似文献
17.
Hsu-Cheng Hsu 《Solid State Communications》2004,131(6):371-375
The coupling strength of the radiative transition of hexagonal ZnO nanowires to the longitudinal optic (LO) phonon polarization field is deduced from temperature dependent photoluminescence spectra. An excitonic polaron formation is discussed to explain why the interaction of free excitons with LO phonons in ZnO nanowires is much stronger than that of bound excitons with LO phonons. The strong exciton-phonon coupling in ZnO nanowires affects not only the Haung-Ray S factor but also the FXA-1LO phonon energy spacing, which can be explained by the excitonic polaron formation. 相似文献
18.
We study the interaction between holes and molecular vibrations on dry DNA by using the extended Firsov's model. The ground state energy, calculated by using two Hilbert spaces, Fock state space and coherent state space, is confirmed. The polaron binding energy, defined with the ground state energy, is 0.014eV, much less than the thermal energy 0.026eV at room temperature 300K, which means that polarons are difficult to form self-trapping at room temperature and Anderson localization will prevent a metallic state on dry DNA. The results are consistent with the available experiments. 相似文献
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We investigate the effect of helix angles on polaron motion in poly-DNA in the framework of a tight binding model. A DNA molecule is supposed to have a uniform or a random distribution of the helix angles. It is found that a polaron moves faster along a DNA molecule with an overwinding helix than that with an unwinding one. In DNA molecule with randomly distributed helix angles, charge transport is suggested to be field-facilitated tunneling between spatial disordered potential wells. 相似文献