Piotr Surówka

If you force water through a narrow neck, the flow speeds up right at the edge, and a whirlpool forms behind the obstacle. Electrons in ultra-clean two-dimensional materials, such as a thin layer of graphene, behave in much the same way.

Magnetic monopoles are like halves of a magnet that cannot exist alone in ordinary materials. But in spin ice, they appear in pairs connected by an invisible thread — a Dirac string. Previously, such monopoles were only seen in artificial systems at room temperature, but their quantum motion remained a mystery.