Macroscopic magnetic monopoles in a 3D-printed mechano-magnet

Abstract

The notion of magnetic monopoles has puzzled physicists since the introduction of Maxwell’s Equations. Famously, Dirac had hypothesized them in the context of quantum mechanics. While they have proved experimentally elusive as elementary particles, the concept has come to describe excitations or topological defects in various material systems, from liquid crystals, to Hall systems, skyrmion lattices, and Bose–Einstein condensates. Perhaps the most versatile manifestation of magnetic monopoles as quasiparticles in matter has been in so-called spin ice materials. There, they represent violations of the ice rule, carry a magnetic charge, and can move freely. Spin ice emergent magnetic monopoles appear at the atomic scale in rare earth pyrochlores or at the nano-scale in lithographically patterned systems. Here we demonstrate for the first time that the notion of magnetic monopoles can be transported at the macroscopic scale. We have built a mechano-magnet realized via 3D-printing, that consists of mechanical rotors on which macroscopic magnets can pivot. By controlling the relative height of the rotors we can achieve different regimes for magnetic monopoles, including the unbound monopole state. We then explore and characterize their field-driven dynamics in different regimes. Despite of several investigation that can be performed in such a macroscopic system, such as insertion of defects, manipulation of rotor friction or dynamics investigation, in the future, integration of our proof of principle in an elastic matrix can lead to novel macroscopic mechano-magnetic materials, to explore unusual piezomagnetism and magnetostriction, with possible applications to actuators and soft-robotics.