Domain dynamics and fluctuations in artificial square ice at finite temperatures

TL;DR

This paper investigates the formation, evolution, and fluctuations of vertex domains in square artificial spin ice at finite temperatures using a combination of mean field theory, Monte Carlo simulations, and experiments, revealing how disorder and interaction strength influence domain dynamics.

Contribution

It introduces a self-consistent mean field model for domain formation and evolution in artificial spin ice, incorporating disorder and fluctuation effects, and compares findings with experimental data.

Findings

Domains form spontaneously due to thermal fluctuations.

Fluctuations bias domain wall dynamics towards shrinking domains.

Interaction strength, controlled by spacing, influences domain behavior.

Abstract

The thermally-driven formation and evolution of vertex domains is studied for square artificial spin ice. A self consistent mean field theory is used to show how domains of ground state ordering form spontaneously, and how these evolve in the presence of disorder. The role of fluctuations is studied, using Monte Carlo simulations and analytical modelling. Domain wall dynamics are shown to be driven by a biasing of random fluctuations towards processes that shrink closed domains, and fluctuations within domains are shown to generate isolated small excitations, which may stabilise as the effective temperature is lowered. Domain dynamics and fluctuations are determined by interaction strengths, which are controlled by inter-element spacing. The role of interaction strength is studied via experiments and Monte Carlo simulations. Our mean field model is applicable to ferroelectric `spin' ice, and we show that features similar to that of magnetic spin ice can be expected, but with different characteristic temperatures and rates.