Equilibrium Field Theory of Magnetic Monopoles in Degenerate Square Spin Ice: Correlations, Entropic Interactions, and Charge Screening Regimes

TL;DR

This paper models magnetic monopoles in degenerate square spin ice as an ensemble with entropic interactions, analyzing their correlations, screening, and structure factors, revealing unique algebraic correlations and pseudo-screening effects.

Contribution

It introduces a theoretical framework for magnetic monopoles in square spin ice, highlighting entropic interactions and screening regimes not previously characterized.

Findings

Effective free energy and correlations match experimental data.

Weak singularities and algebraic correlations identified.

Pseudo-screening regime obscures algebraic screening effects.

Abstract

We describe degenerate square spin as an ensemble of magnetic monopoles coupled via an emergent entropic field that subsumes the effect of the underlying spin vacuum. We compute their effective free energy, entropic interaction, correlations, screening, and structure factors that coincide with the experimental ones. Unlike in pyrochlore ices, a dimensional mismatch between real and entropic interactions leads to weak singularities at the pinch points and algebraic correlations at long distance. This algebraic screening can be, however, camouflaged by a pseudo-screening regime.