Zero temperature coarsening in Ising model with asymmetric second neighbour interaction in two dimensions

TL;DR

This study investigates zero temperature coarsening in a two-dimensional Ising model with asymmetric second-neighbour interactions, revealing complex frozen states, phase behaviors, and universal persistence and exit probabilities across different interaction strengths.

Contribution

It introduces analysis of coarsening dynamics with second-neighbour interactions in 2D Ising models, highlighting new frozen state structures and phase behaviors not seen with only first-neighbour interactions.

Findings

Frozen states persist for all ppa; more complex as ppa increases.

Existence of an iso-energetic active phase for ppa > 2 in finite systems.

Universal persistence and exit probability behaviors observed across ppa values.

Abstract

We consider the zero temperature coarsening in the Ising model in two dimensions where the spins interact within the Moore neighbourhood. The Hamiltonian is given by $H = - \sum_{<i,j>}{S_iS_j} - \kappa \sum_{<i,j'>}{S_iS_{j'}}$ where the two terms are for the first neighbours and second neighbours respectively and $\kappa \geq 0$. The freezing phenomena, already noted in two dimensions for $\kappa=0$, is seen to be present for any $\kappa$. However, the frozen states show more complicated structure as $\kappa$ is increased; e.g. local anti-ferromagnetic motifs can exist for $\kappa>2$. Finite sized systems also show the existence of an iso-energetic active phase for $\kappa > 2$, which vanishes in the thermodynamic limit. The persistence probability shows universal behaviour for $\kappa>0$, however it is clearly different from the $\kappa=0$ results when non-homogeneous initial condition is considered. Exit probability shows universal behaviour for all $\kappa \geq 0$. The results are compared with other models in two dimensions having interactions beyond the first neighbour.