Crystals made out of electrons are real

In 1934, Hungarian-born theoretical physicist Eugene Wigner pondered what would happen if electrons would chill out for once. If they slowed down enough, he figured, the repulsion between their negative charges would start to dominate their behavior. Scrambling to minimize their total energy, electrons would then freeze in place, forming what became known as Wigner crystal.

Wigner’s prediction remained purely theoretical for decades, until Harvard scientists stumbled upon it by accident earlier this year. Working with atomically thin sheets of 2D semiconductors at cryogenic temperatures, a team of physicists noticed that their material stack inexplicably turned into an insulator sometimes.