Theoretical Characterization of the Interface in a Nonequilibrium Lattice System

TL;DR

This paper develops a theoretical framework to understand how nonequilibrium conditions affect interface properties in a kinetic Ising-like model, revealing non-monotonous surface tension and altered interface fluctuations.

Contribution

It introduces a theory for nonequilibrium surface tension and characterizes interface behavior, including fluctuations, in a kinetic Ising model with random spin-flip perturbations.

Findings

Surface tension shows a maximum at finite temperature.

Interface remains rough at zero temperature.

Monte Carlo simulations confirm theoretical predictions.

Abstract

The influence of nonequilibrium bulk conditions on the properties of the interfaces exhibited by a kinetic Ising--like model system with nonequilibrium steady states is studied. The system is maintained out of equilibrium by perturbing the familiar spin--flip dynamics at temperature T with completely--random flips; one may interpret these as ideally simulating some (dynamic) impurities. We find evidence that, in the present case, the nonequilibrium mechanism adds to the basic thermal one resulting on a renormalization of microscopic parameters such as the probability of interfacial broken bonds. On this assumption, we develop theory for the nonequilibrium "surface tension", which happens to show a non--monotonous behavior with a maximum at some finite T. It ensues, in full agreement with Monte Carlo simulations, that interface fluctuations differ qualitatively from the equilibrium case, e.g., the interface remains rough at zero--T. We discuss on some consequences of these facts for nucleation theory, and make some explicit predictions concerning the nonequilibrium droplet structure.