Violation of the Fluctuation-Dissipation Theorem in a Two-Dimensional Ising Model with Dipolar Interactions

TL;DR

This study investigates how the Fluctuation-Dissipation Theorem is violated in a 2D Ising model with competing interactions, revealing that the violation factor behaves similarly to non-frustrated systems despite complex phase behavior.

Contribution

It demonstrates the FDT violation in a dipolar Ising model and analyzes the behavior of the violation factor across different regimes and parameters.

Findings

FDT violation factor X tends to zero in aging regimes

Different phases do not alter the FDT violation behavior

System exhibits domain growth-like dynamics despite complex phases

Abstract

The violation of the Fluctuation-Dissipation Theorem (FDT) in a two-dimensional Ising model with both ferromagnetic exchange and antiferromagnetic dipolar interactions is established and investigated via Monte Carlo simulations. Through the computation of the autocorrelation C(t+t_w,t_w) and the integrated response (susceptibility) functions we obtain the FDT violation factor X(t+t_w,t_w) for different values of the temperature, the waiting time t_w and the quotient delta=J_0/J_d, J_0 and J_d being the strength of exchange and dipolar interactions respectively. For positive values of delta this system develops a striped phase at low temperatures, in which the non-equilibrium dynamics presents two different regimes. Our results show that such different regimes are not reflected in the FDT violation factor, where X goes always to zero for high values of t_w in the aging regime, a result that appears in domain growth processes in non-frustrated ordered systems.