Ferromagnetic Coulomb phase in classical spin ice

TL;DR

This paper demonstrates the existence of a ferromagnetically ordered Coulomb phase in classical spin ice under uniaxial distortion, revealing a novel coexistence of magnetic order and spin liquid behavior.

Contribution

It introduces a microscopic model showing a ferromagnetic Coulomb phase in spin ice, supported by theoretical arguments and Monte Carlo simulations, and relates it to superfluid phases in lattice bosons.

Findings

Confirmation of ferromagnetic Coulomb phase via Monte Carlo simulations

Identification of deconfined monopoles with magnetic order

Signatures in neutron scattering and critical behavior analysis

Abstract

Spin ice is a frustrated magnetic system that at low temperatures exhibits a Coulomb phase, a classical spin liquid with topological order and deconfined excitations. This work establishes the presence of a Coulomb phase with coexisting ferromagnetic order in a microscopic model of classical spin ice subject to uniaxial lattice distortion. General theoretical arguments are presented for the presence of such a phase, and its existence is confirmed using Monte Carlo results. This example is used to illustrate generic properties of spin liquids with magnetic order, including deconfinement of monopoles, signatures in the neutron-scattering structure factor, and critical behavior at phase transitions. An analogous phase, a superfluid with spontaneously broken particle-hole symmetry, is demonstrated in a model of hard-core lattice bosons, related to spin ice through the quantum-classical correspondence.