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arXiv 2401.04342cond-mat.stat-mech
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缓慢淬火经典Ising链中的Kibble-Zurek标度与粗化定律

Kibble-Zurek scalings and coarsening laws in slowly quenched classical Ising chains

Lakshita Jindal, Kavita Jain

AI总结:

研究一维经典Ising模型在有限时间淬火至零温时的缺陷密度动力学,发现其由粗化与Kibble-Zurek机制共同决定,并给出了Glauber链的精确解与Kawasaki链的数值验证。

摘要:

我们考虑一维经典铁磁Ising模型,在有限时间内使用Glauber或Kawasaki动力学将其从低温淬火至零温。先前关于有限时间淬火的大多数工作假设系统初始处于平衡态,并关注淬火结束时的过剩缺陷密度,该密度随淬火时间按Kibble-Zurek指数代数衰减。在此,我们感兴趣的是理解Kibble-Zurek标度不成立的条件,并阐明缺陷密度的完整动力学。我们发现,根据初始条件和淬火时间的不同,缺陷密度的动力学可由粗化和/或涉及绝热演化和Kibble-Zurek动力学的标准有限时间淬火动力学来表征;这些动力学相之间交叉的时间尺度由粗化时间和稳态弛豫时间决定。因此,淬火结束时的缺陷密度要么是常数,要么遵循粗化定律或Kibble-Zurek标度衰减。对于Glauber链,我们提出了一个低温标度理论,并找到了各种初始条件下最终缺陷密度的精确表达式。对于粗化和稳态动力学指数不同的Kawasaki链,我们数值验证了上述发现,并考察了不等动力学指数的影响。

英文摘要:

We consider a one-dimensional classical ferromagnetic Ising model when it is quenched from a low temperature to zero temperature in finite time using Glauber or Kawasaki dynamics. Most of the previous work on finite-time quenches assume that the system is initially in equilibrium and focus on the excess defect density at the end of the quench which decays algebraically in quench time with Kibble-Zurek exponent. Here we are interested in understanding the conditions under which the Kibble-Zurek scalings do not hold and in elucidating the full dynamics of the defect density. We find that depending on the initial conditions and quench time, the dynamics of the defect density can be characterized by coarsening and/or the standard finite-time quench dynamics involving adiabatic evolution and Kibble-Zurek dynamics; the time scales for crossover between these dynamical phases are determined by coarsening time and stationary state relaxation time. As a consequence, the defect density at the end of the quench is either a constant or decays following coarsening laws or Kibble-Zurek scaling. For the Glauber chain, we formulate a low temperature scaling theory and find exact expressions for the final defect density for various initial conditions. For the Kawasaki chain where the dynamic exponents for coarsening and stationary state dynamics are different, we verify the above findings numerically and also examine the effect of unequal dynamic exponents.

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