Cannas Sergio A, Michelon Mateus F, Stariolo Daniel A, Tamarit Francisco A
Instituto de Física de la Facultad de Matemática, Astronomía y Física (IFFAMAF-CONICET), Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Nov;78(5 Pt 1):051602. doi: 10.1103/PhysRevE.78.051602. Epub 2008 Nov 14.
We study the dynamical behavior of a square lattice Ising model with exchange and dipolar interactions by means of Monte Carlo simulations. After a sudden quench to low temperatures, we find that the system may undergo a coarsening process where stripe phases with different orientations compete, or alternatively it can relax initially to a metastable nematic phase and then decay to the equilibrium stripe phase through nucleation. We measure the distribution of equilibration times for both processes and compute their relative probability of occurrence as a function of temperature and system size. This peculiar relaxation mechanism is due to the strong metastability of the nematic phase, which goes deep into the low-temperature stripe phase. We also measure quasiequilibrium autocorrelations in a wide range of temperatures. They show a distinct decay to a plateau that we identify as due to a finite fraction of frozen spins in the nematic phase. We find indications that the plateau is a finite-size effect. Relaxation times as a function of temperature in the metastable region show super-Arrhenius behavior, suggesting a possible glassy behavior of the system at low temperatures.
我们通过蒙特卡罗模拟研究了具有交换和偶极相互作用的方形晶格伊辛模型的动力学行为。在突然骤冷至低温后，我们发现系统可能会经历一个粗化过程，其中不同取向的条纹相相互竞争，或者它也可以先弛豫到亚稳向列相，然后通过成核衰变为平衡条纹相。我们测量了这两个过程的平衡时间分布，并计算了它们作为温度和系统尺寸函数的相对发生概率。这种奇特的弛豫机制是由于向列相的强亚稳性，它深入到低温条纹相中。我们还在很宽的温度范围内测量了准平衡自相关。它们显示出明显衰减到一个平台，我们认为这是由于向列相中有限比例的冻结自旋所致。我们发现有迹象表明该平台是一种有限尺寸效应。亚稳区域中弛豫时间作为温度的函数表现出超阿仑尼乌斯行为，这表明系统在低温下可能具有玻璃态行为。
