三模型随机场对一维量子Ising模型动力学性质的调控

量子自旋系统在外磁场下的动力学性质一直是凝聚态理论和统计物理研究的热点.本文利用递推关系方法,通过计算系统的自旋关联函数及其对应的谱密度,研究了三模型随机外场对一维量子Ising模型动力学性质的调控效应.在三模型随机横场下,利用r分支引入了非磁性杂质,研究表明:非磁性杂质使得系统的低频响应得到保持,中心峰值行为更加明显;非磁性杂质与横场之间的竞争能激发出新的频率响应,呈现多峰行为;但较多的非磁性杂质最终会限制系统对横场的响应.此外,研究还发现随机横场的三模分布参数满足qB_q=pB_p这一条件,是使中心峰值行为得到保持的有利条件.在三模型随机纵场下, r分支仅仅起到调节纵场强度的作用,且r分支所占比重的增大不利于低频响应,与三模型随机横场下r分支的调控作用是相反的.     

共轭聚合物中均匀无序对极化子输运动力学的影响

基于扩展的Su-Schrieffer-Heeger紧束缚模型和非绝热动力学方法, 研究了共轭聚合物材料中均匀无序效应对极化子输运动力学的影响. 研究发现: 极化子的动力学输运过程由外加电场和均匀无序效应共同决定; 在大部分电场范围下, 均匀无序效应对极化子输运的影响不太明显, 几乎可以忽略; 但在弱电场下, 均匀无序效应不利于极化子输运. 与高斯型无序效应下极化子的输运过程相比, 具有均匀无序的薄膜形貌更有利于极化子输运.     

Injection and transport of electric charge in a metal/copolymer structure

The dynamical processes of the electric charge injection and transport from a metal electrode to the copolymer are investigated by using a nonadiabatic dynamic approach. The simulations are performed within the framework of an extended version of the one-dimensional Su-Schrieffer-Heeger (SSH) tight-binding model. It is found that the electric charge can be injected into the copolymer by increasing the applied voltage. For different structures of the copolymer, the critical voltage biases are different and the motion of the injected electric charge in the copolymer varies obviously. For the copolymer with a barrier-well-barrier configuration, the injected electric charge forms a wave packet due to the strong electron-lattice interaction in the barrier, then comes into the well and will be confined in it under a weak electric field. Under a medium electric field, the electric charge can go across the interface of two homopolymers and enter into the other potential barrier. For the copolymer with a well-barrier-well configuration, only under strong enough electric field can the electric charge transfer from the potential well into the barrier and ultimately reach a dynamic balance.     

次近邻作用对随机量子Ising系统动力学性质的影响

利用递推关系方法在高温极限下研究了具有次近邻自旋耦合相互作用的一维随机量子Ising系统的动力学性质,求解了系统的自关联函数及谱密度.假设自旋耦合参量或横向磁场满足双高斯分布,研究发现当随机变量的标准偏差σJ(σB)较小时系统的动力学性质存在从集体模行为到中心峰值行为的交跨效应,当σJ(σB)较大时,交跨效应消失,系统只表现一种动力学行为.讨论了次近邻相互作用对系统动力学性质的影响,发现当KiJ2i(Ji和Ki分别为近邻和次近邻相互作用)时次近邻相互作用对系统动力学性质的影响不太明显,可以忽略;当Ki2Ji时,次近邻相互作用使得系统的中心峰值行为表现得更加明显,或使其集体模行为呈减弱的趋势.     

共轭聚合物中链内无序效应对极化子输运的影响

基于扩展的Su-Schrieffer-Heeger紧束缚模型, 利用非绝热动力学方法研究了链内无序效应对共轭聚合物中极化子输运机制的影响. 研究发现, 极化子的输运由外加电场和链内无序效应共同作用的结果所决定. 在一般情况下, 链内无序效应不利于极化子的输运, 但随着电场强度的增大, 无序对极化子输运的影响减小. 关键词： 共轭聚合物 极化子输运 链内无序     

Spin transport properties for B-doped zigzag silicene nanoribbons with different edge hydrogenations

Exploring silicon-based spin modulating junction is one of the most promising areas of spintronics.Using nonequilibrium Green's function combined with density functional theory,a set of spin filters of hydrogenated zigzag silicene nanoribbons is designed by substituting a silicon atom with a boron one and the spin-correlated transport properties are studied.The results show that the spin polarization can be realized by structural symmetry breaking induced by boron doping.Remarkably,by tuning the edge hydrogenation,it is found that the spin filter efficiency can be varied from 30%to 58%.Moreover,it is also found and explained that the asymmetric hydrogenation can give rise to an obvious negative differential resistance which usually appears at weakly coupled junction.These findings indicate that the boron-doped ZSiNR is a promising material for spintronic applications.