随机外磁场对一维Blume-Capel模型动力学性质的影响

近几十年来,量子自旋系统的动力学性质引起了人们的广泛关注,随着研究的不断深入,随机自旋系统的性质受到了人们的重视. 利用递推关系式方法研究了高温极限下随机外磁场中自旋s=1的一维Blume-Capel模型的动力学性质, 通过计算自旋自关联函数和相应的谱密度,探讨了外场对系统动力学行为的影响.研究表明,在无晶格场的情况下, 当外场满足双模分布时,系统的动力学性质存在从中心峰值行为到集体模行为的交跨效应.当外场满足Gauss分布, 标准偏差较小时,系统也存在交跨效应;标准偏差足够大时,系统只表现为无序行为. 另外还研究了晶格场对系统动力学性质的影响,发现晶格场的存在减弱了系统的集体模行为.

Effects of random external fields on the dynamics of the one-dimensional Blume-Capel model

The dynamical properties of quantum spin systems have received a great deal of theoretical and experimental attention in the past decades. Only recently, has much attention been paid to the random quantum spin systems. In this paper the effect of random external field on the dynamics of one-dimensional Blume-Capel model with s = 1 in the high-temperature limit is investigated by using the recurrence relations method. The spin autocorrelation function as well as the corresponding spectral density of the system is calculated in the presence of the field that satisfies two types of distributions. When the single-ion anisotropy takes 0, for the bimodal distribution, the dynamics of the system behaves as a crossover from a central peak behavior to a collective mode one. For the Gaussian distribution, when the standard deviation is small, the dynamical behavior of the system also exhibits a crossover; when the standard deviation is large enough, the system only shows a disordered behavior. We also discuss the effect of the single-ion anisotropy on the dynamical property of the system, and find that the collective-mode behavior becomes weaker as the single-ion anisotropy exists.