Magnetic multipole analysis of kagome and artificial ice dipolar arrays

TL;DR

This paper investigates the phase diagram of dipolar arrays on kagome and square lattices, revealing multiple kagome ice regimes, entropy plateaux, and complex monopole interactions, advancing understanding of artificial spin ice systems.

Contribution

It provides a detailed analysis of phase behavior and monopole interactions in dipolar arrays, introducing a charge-based theory to explain entropy features.

Findings

Identified two distinct kagome ice regimes, including a disordered and an algebraic phase.

Discovered entropy plateaux in the near-touching island limit, explained by magnetic charge theory.

Showed monopoles in square ice experience both Coulomb and entropic interactions.

Abstract

We analyse an array of linearly extended monodomain dipoles forming square and kagome lattices. We find that its phase diagram contains two (distinct) finite-entropy kagome ice regimes - one disordered, one algebraic - as well as a low-temperature ordered phase. In the limit of the islands almost touching, we find a staircase of corresponding entropy plateaux, which is analytically captured by a theory based on magnetic charges. For the case of a modified square ice array, we show that the charges ('monopoles') are excitations experiencing two distinct Coulomb interactions: a magnetic 'three-dimensional' one as well as a logarithmic `two dimensional' one of entropic origin.