Macroscopic Magnetic Monopoles in a 3D-Printed Mechano-Magnet

摘要

The notion of magnetic monopoles has puzzled physicists since the introduction of Maxwell's Equations and 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 condensate. 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 unbound. Spin ice emergent magnetic monopoles appear at the atomic scale in rare earth pyrochlores or at the nano-scale in artificial spin ices 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 free monopole state. We then explore their driven dynamics under field. 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 applications to actuators and soft-robotics.