Off equilibrium dynamics in 2d-XY system

TL;DR

This paper investigates the non-equilibrium dynamics of the 2D XY model, focusing on autocorrelation and response functions after quenches, revealing insights into fluctuation-dissipation violations in critical phases.

Contribution

It provides a detailed Monte Carlo analysis of the time evolution of autocorrelation and response functions in the 2D XY model after quenches, highlighting the behavior of fluctuation-dissipation ratios.

Findings

Autocorrelation and response functions evolve distinctly after quenches.

The fluctuation-dissipation ratio tends to vanish in the asymptotic regime.

The slope of the susceptibility/correlation plot varies with temperature.

Abstract

We study the non-equilibrium time evolution of the classical XY spin model in two dimensions. The two-time autocorrelation and linear response functions are considered for systems initially prepared in a high temperature state and in a completely ordered state. After a quench into the critical phase, we determine, via Monte Carlo simulations, the time-evolution of these quantities and extract the temperature dependence of the slope of the parametric plot susceptibility/correlation in the asymptotic regime. This slope is usually identified with the infinite fluctuation-dissipation ratio which measures the violation to the equilibrium fluctuation-dissipation theorem. However, a direct measure of this ratio leads to a vanishing value.