Field-Induced Magnetic Monopole Plasma in Artificial Spin Ice

TL;DR

This paper demonstrates that artificial spin ice can host high-density, plasma-like regimes of mobile magnetic monopoles, revealing their intrinsic dynamics and opening new avenues for studying magnetic charges in synthetic materials.

Contribution

It shows that square artificial spin ice can support monopole plasma phases with tunable densities and dynamics, advancing understanding of magnetic monopole behavior in engineered systems.

Findings

Monopole plasma regimes exist in specific phase diagram regions.

Monopole kinetics are mostly diffusive in the plasma phase.

Passive noise measurements reveal intrinsic monopole dynamics.

Abstract

Artificial spin ices (ASIs) are interacting arrays of lithographically-defined nanomagnets in which novel frustrated magnetic phases can be intentionally designed. A key emergent description of fundamental excitations in ASIs is that of magnetic monopoles -- mobile quasiparticles that carry an effective magnetic charge. Here we demonstrate that the archetypal square ASI lattice can host, in specific regions of its magnetic phase diagram, high-density plasma-like regimes of mobile magnetic monopoles. By passively "listening" to spontaneous monopole noise in thermal equilibrium, we reveal their intrinsic dynamics and show that monopole kinetics are minimally correlated (that is, most diffusive) in the plasma phase. These results open the door to on-demand monopole regimes having field-tunable densities and dynamic properties, thereby providing a new paradigm for probing the physics of effective magnetic charges in synthetic matter.