String Phase in an Artificial Spin Ice

TL;DR

This study investigates string-like excitations in a classical artificial spin ice system, revealing that their length distribution follows a Boltzmann law and that topological string descriptions are applicable beyond quantum models.

Contribution

It demonstrates that classical frustrated magnetic systems can be effectively described using emergent string frameworks, extending the concept beyond quantum topological matter.

Findings

String length distribution follows Boltzmann statistics.

Experimental results align with theoretical predictions.

Topological string descriptions apply to classical systems.

Abstract

One-dimensional strings of local excitations are a fascinating feature of the physical behavior of strongly correlated topological quantum matter. Here we study strings of local excitations in a classical system of interacting nanomagnets, the Santa Fe Ice geometry of artificial spin ice. We measured the moment configuration of the nanomagnets, both after annealing near the ferromagnetic Curie point and in a thermally dynamic state. While the Santa Fe Ice lattice structure is complex, we demonstrate that its disordered magnetic state is naturally described within a framework of emergent strings. We show experimentally that the string length follows a simple Boltzmann distribution with an energy scale that is associated with the system's magnetic interactions and is consistent with theoretical predictions. The results demonstrate that string description and associated topological characteristics are not unique to quantum models but can also provide a simplifying description of complex classical systems with non-trivial frustration.