Controlled creation and annihilation of stringless robust emergent magnetic monopoles in artificial spin ice

TL;DR

This paper demonstrates the controlled creation and stabilization of isolated magnetic monopole-like states in artificial spin ice, enabling new studies of monopole physics in solid-state systems.

Contribution

It introduces a method to stabilize single emergent magnetic monopoles in artificial spin ice using external magnetic fields, avoiding paired antimonopoles.

Findings

Controlled monopole stabilization achieved in square ASI vertices.

Experimental results supported by Monte Carlo simulations.

Potential for studying monopole electrodynamics in solid-state environments.

Abstract

Magnetic analogue of an isolated free electric charge, i.e., a magnet with a single north or south pole, is a long sought-after particle which remains elusive so far. In magnetically frustrated pyrochlore solids, a classical analogue of monopole was observed as a result of excitation of spin ice vertices. Direct visualization of such excitations were proposed and later confirmed in analogous artificial spin ice (ASI) systems of square as well as Kagome geometries. However, such charged vertices are randomly created as they are thermally driven and are always associated with corresponding emergent antimonopoles of equal and opposite charges connected by observable strings. Here, we demonstrate a controlled stabilisation of a robust isolated emergent monopole state in individual square ASI vertices by application of an external magnetic field. The excitation conserves the magnetic charge without the involvement of a corresponding antimonopole. Well supported by Monte Carlo simulations our experimental results enable, in absence of a true elemental magnetic monopole, creation of electron vortices and studying electrodynamics in presence of a monopole field in a solid state environment.