Ever since quantum mechanics first described particles, like electrons, as rippling waves, researchers have wondered if those waves could be trapped in place. Writing today in Science a century later, a team of Columbia University researchers reports waves of electrons becoming trapped for the first time in a metal called Pd₅AlI₂

“Quantum mechanics predicts that an electron wave can, theoretically, remain trapped even when there are infinitely many paths for it to escape. This effect is known from light waves, but it has never been seen before for electrons,” said Raquel Queiroz, a theoretical physicist at Columbia. It was a surprising discovery, and one that opens new possibilities for manipulating quantum states in metals.