The dynamics of one-dimensional random quantum XY system with Dzyaloshinskii-Moriya interaction

In this paper,the effects of random variables on the dynamics of the s = 1/2 XY model with the Dzyaloshinskii-Moriya interaction are studied.By means of the recurrence relation method in the high-temperature limit,we calculate the spin autocorrelation functions as well as the corresponding spectral densities for the cases that the exchange couplings between spins or external magnetic fields satisfy the double-Gaussian distribution.It is found that when the standard deviation of random exchange coupling δJ(or the standard deviation of random external field δB) is small,the dynamics of the system undergoes a crossover from a collective-mode behavior to a central-peak one.However,when δJ(or δB) is large,the crossover vanishes,and the system shows a central-peak behavior or the most disordered one.We also analyze the cases in which the exchange couplings or the external fields satisfy the bimodal and the Gaussian distributions.Our results show that for all the cases considered,the dynamics of the above system is similar to that of the one-dimensional random XY model.     

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首届全国中学英语教师(高师学生)英语教学技能大赛试题分为英语语言技能部分和教学技能部分.第一部分重在考查受试者的专业水平;第二部分则测验考生的教学能力.本文对试卷进行了逐项分析,研究了试题的涉及面、包容性、分值布局、合理度、信度、效度以及出题思路等.     

Dynamics of one-dimensional random quantum XY system with Dzyaloshinskii–Moriya interaction

In this paper, the effects of random variables on the dynamics of the s=1/2 XY model with the Dzyaloshinskii-Moriya interaction are studied. By means of the recurrence relation method in the high-temperature limit, we calculate the spin autocorrelation functions as well as the corresponding spectral densities for the cases that the exchange couplings between spins or external magnetic fields satisfy the double-Gaussian distribution. It is found that when the standard deviation of random exchange coupling δ_j (or the standard deviation of random external field δ_B) is small, the dynamics of the system undergoes a crossover from a collective-mode behavior to a central-peak one. However, when δ_J (or δ_B) is large, the crossover vanishes, and the system shows a central-peak behavior or the most disordered one. We also analyze the cases in which the exchange couplings or the external fields satisfy the bimodal and the Gaussian distributions. Our results show that for all the cases considered, the dynamics of the above system is similar to that of the one-dimensional random XY model.