Observing Magnetic Monopoles in Spin Ice using Electron Holography

TL;DR

This paper demonstrates that electron holography can directly observe magnetic monopoles and emergent electric fields in spin ice materials, providing a new experimental approach to study these exotic quasiparticles.

Contribution

It introduces electron holography as a method to detect magnetic monopoles and electric fields in spin ice, supported by experiments on artificial spin ice and simulations on pyrochlore spin ice.

Findings

Holography can measure local magnetic charge in artificial spin ice.

Holography can resolve magnetic monopoles and their dynamics in pyrochlore spin ice.

Observation of emergent electric fields is feasible with high phase resolution electron microscopes.

Abstract

While there is compelling evidence for the existence of magnetic monopoles in spin ice, the direct observation of a point-like source of magnetic field in these systems remains an open challenge. One promising approach is electron holography, which combines atomic-scale resolution with extreme sensitivity to magnetic vector potentials, through the Aharonov-Bohm effect. Here we explore what holography can teach us about magnetic monopoles in spin ice, through experiments on artificial spin ice, and numerical simulations of pyrochlore spin ice. In the case of artificial spin ice, we show that holograms can be used to measure local magnetic charge. For pyrochlore spin ice, we demonstrate that holographic experiments are capable of resolving both magnetic monopoles and their dynamics, including the emergence of electric fields associated with fluctuations of closed loops of spins. These results establish that the observation of both magnetic monopoles and emergent electric fields in pyrochlore spin ice is a realistic possibility in an electron microscope with sufficiently--high phase resolution.