Zero temperature ordering dynamics in two dimensional BNNNI model

Abstract

We investigate the dynamics of a two dimensional bi-axial next nearest neighbour Ising (BNNNI) model following a quench to zero temperature. The Hamiltonian is given by $H = -J_0\sum_{i,j=1}^L [(S_{i,j}S_{i+1,j}+S_{i,j}S_{i,j+1}) -\kappa (S_{i,j}S_{i+2,j} + S_{i,j}S_{i,j+2})]$ . For $\kappa <1$, the system does not reach the equilibrium ground state and keep evolving in active states for ever. For $\kappa \geq 1$, though the system reaches a final state, but it do not reach the ground state always and freezes to a striped state with a finite probability like two dimensional ferromagnetic Ising model and ANNNI model. The overall dynamical behaviour for $\kappa > 1$ and $\kappa =1$ is quite different. The residual energy decays in a power law for both $ \kappa >1$ and $\kappa =1$ from which the dynamical exponent $z$ have been estimated. The persistence probability shows algebraic decay for $\kappa > 1$ with an exponent $\theta = 0.22 \pm 0.002$ while the dynamical exponent for ordering $z=2.33\pm 0.01$. For $\kappa =1$, the system belongs to a completely different dynamical class with $\theta = 0.332 \pm 0.002$ and $z=2.47\pm 0.04$. We have computed the freezing probability for different values of $\kappa$. We have also studied the decay of autocorrelation function with time for different regime of $\kappa$ values. The results have been compared with that of the two dimensional ANNNI model.