Interplay between coarsening and nucleation in an Ising model with dipolar interactions

TL;DR

This study investigates the complex relaxation dynamics of a dipolar Ising model, revealing coarsening, metastability, nucleation, and potential glassy behavior through Monte Carlo simulations.

Contribution

It uncovers the interplay between coarsening and nucleation processes, highlighting the metastable nematic phase and its impact on relaxation mechanisms in the model.

Findings

Metastable nematic phase influences relaxation pathways.

Super-Arrhenius temperature dependence suggests glassy dynamics.

Finite size effects affect the observed plateau in autocorrelations.

Abstract

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 in the low temperature stripe phase. We also measure quasi-equilibrium 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.