发表机构
Dipartimento di Fisica dell’Università di Roma “La Sapienza”; INFN, Sezione di Roma; Dipartimento di Fisica dell’Università di Pisa; INFN（罗马大学物理系; 意大利国家核物理研究所罗马分部; 比萨大学物理系; 意大利国家核物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究分析伊辛系统跨越磁一级相变淬火后的非平衡动力学，发现有限临界时间出现动态逾渗转变，其临界行为与类旋节线磁化行为相关，且该现象在缓慢变化磁场协议中同样存在。
AI 中文摘要
我们分析了铁磁伊辛类系统在外部均匀磁场$h$的突然和缓慢变化驱动下，跨越其低温磁一级相变（FOT）线时的非平衡弛豫动力学。作为一个典型例子，我们考虑一个二维伊辛系统，通过将$h$从$h_i<0$突然淬火到$h>0$，驱动其跨越低温FOT线，从而诱导从负磁化相到正磁化相的转变。我们展示了在淬火后演化过程中，对于有限（足够小）的$h$值，在有限临界时间$t_c(h)$处出现动态逾渗转变，其特征是最大正自旋团簇的逾渗和最大负自旋团簇的反逾渗。这种非平衡逾渗转变表现出与标准随机逾渗情形相同的有限尺寸标度行为。然而，虽然逾渗团簇的分形维数与随机逾渗值一致，但控制趋近临界态的指数不同，且依赖于$h$。我们还表明，逾渗转变标志着从亚稳的负磁化相到稳定的正磁化相的过渡。因此，在小$h$极限下，逾渗临界行为与磁化的类旋节线行为相关，这意味着逾渗时间$t_c(h)$表现出对$h$的类旋节线指数依赖。逾渗转变的存在可能是磁性伊辛类FOT中的普遍现象。例如，我们在涉及磁场缓慢变化驱动跨越FOT线的动态（Kibble-Zurek类）协议中观察到类似行为。
英文摘要
We analyze the out-of-equilibrium relaxational dynamics of ferromagnetic Ising-like systems driven across their low-temperature magnetic first-order transition (FOT) line, by sudden and slow variations of an external homogenous magnetic field $h$. As a paradigmatic example, we consider a two-dimensional Ising system driven across its low-temperature FOT line by suddently quenching $h$ from $h_i<0$ to $h>0$, inducing a transition from the negatively to the positively magnetized phase. We show the emergence of a dynamic percolation transition at a finite critical time $t_c(h)$ along the post-quench evolution for finite (sufficiently small) values of $h$, which is marked by the percolation of the largest positive-spin cluster and the antipercolation of the largest negative-spin cluster. This out-of-equilibrium percolation transition displays a finite-size scaling behavior as in the standard random-percolation case. However, while the fractal dimension of the percolating clusters is consistent with the random-percolation value, the exponent controlling the approach to criticality differs and depends on $h$. We also show that the percolation transition marks the passage from the metastable negatively-magnetized phase to the stable positively-magnetized one. Therefore, in the small-$h$ limit, the percolation critical behavior is related to the spinodal-like behavior of the magnetization, implying that the percolation time $t_c(h)$ exhibits a spinodal-like exponential dependence on $h$. The existence of percolation transitions is likely a generic phenomenon at magnetic Ising-like FOTs. For example, we observe an analogous behavior in dynamic (Kibble-Zurek-like) protocols entailing slow variations of the magnetic field driving the crossing of the FOT line.
Comments15 pages
