A Child’s Puzzle Helped Uncover How Magnets Really Work

To fully understand how the behavior of individual particles leads to the collective phenomenon of ferromagnetism, you would need to keep track of the wave function of every electron in a system as it continually reshapes every other electron’s wave function through their mutual interactions. Their result, called the Nagaoka-Thouless theorem (also Nagaoka’s theorem), relies on an idealized system of electrons on an atomic lattice. Just swap the labels on the tiles from numbers to up or down spins, and the puzzle becomes equivalent to a Nagaoka ferromagnet, with a hole that moves through a lattice of electrons.

Source: www.wired.com