Glassy Dynamics in Random Spin Systems

随机自旋系统中的玻璃动力学

• 批准号: 12640367
• 负责人: TAKAYAMA Hajime
• 金额: $ 1.28万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640367/
• 关键词: glassy dynamics; spin glass; aging phenomena; droplet picture; zero-field-cooled magnetization; memory effect; chaos effect; Monte Carlo method; 液滴理論; 熱活性化過程; 臨界緩和; 温度シフト過程; メモリー効果; 磁場シフト過程

Aging phenomena in spin glasses, the most typical glassy dynamics, have been extensively studied. Their various aspects in the Edwards-Anderson (EA) model have been numerically examined by the Monte Carlo method. Most of the results simulated turn out to be well interpreted by means of the droplet picture : the aging phenomena associate with the extremely slow equilibration which is due to thermally-activated processes and is represented in terms of the growth law of the spin-glass (SG) coherence length (or the mean size of SG domains), R (tw), at time tw after rapid quench of the system to the low-temperature SG phase. Furthermore we have confirmed the scaling expressions of various quantities in terms of R (tw) and L (t), where the latter is the mean size of droplets excited within time scale of t. More explicitly, we have found the following results.1) By the simulation on the zero-field-cooled magnetization (ZFCM), R (tw) is found to cumulatively grow even when the temperature is c … More hanged within the SG phase. When its growth law extracted from the simulation is directly applied to the corresponding experimental ZFCM measurement whose time scale is larger by more than 10 orders of magnitude than the simulation, the ZFCM data turn out to lie on a universal function of R (tw). This is the first direct and quantitative coincidence between experiment and simulation on aging phenomena. 2) The isothermal aging process in the 4-dimensional (4D) EA model has been intensively studied, and it has been found for the first time that the most of the results, including the growth law of R (tw), are well described by the droplet theory. Furthermore, the droplet excitation energy is found to become anomalously small in the time range where R (tw) and L (t) are comparable. We have argued that this fact is the origin of difference between the ZFCM and field-cooled magnetization observed experimentally. 3) The temperature-shift aging process in the 3D EA model has been examined through the ac susceptibility, and various scaling expressions have been confirmed in terms of R (tw) and L (t) simulated. The precursor of the chaos (rejuvenation) effect has been also found for the first time in simulation. Less

自旋玻璃中的老化现象是最典型的玻璃动力学现象，已被广泛研究。它们在Edwards-Anderson（EA）模型中的各个方面已经用Monte Carlo方法进行了数值研究。大部分的模拟结果被证明是很好的解释，通过液滴图片：老化现象与非常缓慢的平衡，这是由于热激活过程，并表示在自旋玻璃（SG）的相干长度（或SG域的平均尺寸），R（tw）的增长规律，在时间tw后，系统的快速淬火到低温SG相。此外，我们还确定了各种量在R（tw）和L（t）方面的标度表达式，其中L（t）是在时间尺度t内激发的液滴的平均尺寸。通过对零场冷却磁化强度（ZFCM）的模拟，发现即使在温度为20 ℃时，R（tw）也会累积增长 ...更多信息 在SG阶段挂起。当从模拟中提取的增长规律直接应用到相应的实验ZFCM测量中时，其时间尺度比模拟大10个数量级以上，ZFCM数据位于R（tw）的一个普适函数上。这是第一次直接和定量的一致性之间的实验和模拟老化现象。2)对4维EA模型中的等温时效过程进行了深入研究，首次发现液滴理论能很好地描述大部分结果，包括R（tw）的增长规律。此外，发现液滴激发能量在R（tw）和L（t）相当的时间范围内变得异常小。我们认为，这一事实是ZFCM和场冷磁化实验观察到的差异的起源。3)通过交流磁化率研究了3D EA模型中的温移时效过程，并根据模拟的R（tw）和L（t）证实了各种标度表达式。在模拟中还首次发现了混沌（返老还童）效应的前兆。少

项目成果

L.W.Bernardi: "Aging of the Zero-Field-Cooled Magnetization in Ising Sping Glasses : Experiment and Numerical Simulation"Phys.Rev.Lett.. 86. 720-723 (2001)

L.W.Bernardi：“伊辛望远镜中零场冷却磁化的老化：实验和数值模拟”Phys.Rev.Lett.. 86. 720-723 (2001)

L.W.Bernardi: "Aging of the Zero-Field-Cooled Magnetization in Ising Spin Glasses : Experiment and Numerical Simulation"Phys. Rev. Lett.. 86. 720-723 (2001)

L.W.Bernardi：“伊辛自旋玻璃中零场冷却磁化的老化：实验和数值模拟”物理。

T. Komori, H. yoshino, and H. Takayama: "Numerical Study on Aging Dynamics in the 3D Ising Spin-Glass Model. II. Quasi-Equilibrium Regime of Spin Auto-Correlation Function"J. Phys. Soc. Jpn. 69. 1192-1201 (2000)

T. Komori、H. yoshino 和 H. Takayama：“3D Ising 自旋玻璃模型中老化动力学的数值研究。II. 自旋自相关函数的准平衡状态”J。

T.Komori: "Numerical Study on Aging Dynamics in the 3D Ising Spin-Glass Model. II. Quasi-Equilibrium Regime of Spin Auto-Correlation Function"J. Phys. Soc. Jpn.. 69. 1192-1201 (2000)

T.Komori：“3D Ising 自旋玻璃模型中老化动力学的数值研究。II.自旋自相关函数的准平衡状态”J。

T.Komori: "Numerical Study on Aging Dynamics in Ising Spin-Glass Models : Temperature-Change Protocols"J.Phys.Soc.Jpn.Suppl.. 69A. 228-237 (2000)

T.Komori：“伊辛旋转玻璃模型中老化动力学的数值研究：温度变化协议”J.Phys.Soc.Jpn.Suppl.. 69A。