次近邻作用对随机量子Ising系统动力学性质的影响  

Effects of next-nearest-neighbor interactions on the dynamics of random quantum Ising model

作　　者：袁晓娟[1,2] 赵邦宇 陈淑霞[1] 孔祥木[1] 

机构地区：[1]山东省激光偏光与信息技术重点实验室,曲阜师范大学物理工程学院,曲阜273165 [2]山东大学物理学院,晶体材料国家重点实验室,250100 [3]积成电子股份有限公司,济南250100

出　　处：《物理学报》2010年第3期1499-1506,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10775088);山东省自然科学基金(批准号:Y2006A05)资助的课题~~

摘　　要：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Ki<J2i(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Ki>2Ji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.The dynamics of one-dimensional random quantum Ising model with both nearest-neighbor and next-nearest-neighbor （NNN） interactions is investigated in the high temperature limit by the method of recurrence relations. Spin autocorrelations and the corresponding spectral densities of the system are calculated. Supposing that the exchange couplings （or the transverse fields） satisfy the double-Ga ussian distribution, the effects of this distribution on the dynamics of the system is studied. The results show that the dynamics of the system undergoes a crossover from a collective-mode behavior to a central-peak one when the standard deviations σ_J（or σ_B）of the random variables are small and there is no crossover when σ_J（or σ_B）are large. Meanwhile, the effects of NNN interactions on the dynamics of the system are studied. It is found that the central-peak behavior becomes more obvious and the collective-mode behavior becomes weaker as K_i increase, especially when K_iJ_i/2 （J_i an d K_i are exchange couplings of the NN and NNN interactions, respectively）. However, the effects are small when the NNN interactions are weak （K_iJ_i/ 2）.

关 键 词：随机量子Ising模型 递推关系方法 自关联函数 谱密度 

分 类 号：N941.3[自然科学总论—系统科学]